Gems & Gemology

4 C’s

Diamonds, by nature of their unique characteristics, can be evaluated much more precisely than other gems. Their extreme hardness allows ...
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16th Century Plate - Lapidus.

A Brief History of Gemstone Writings

from Gems in Myth, Legend and Lore by Bruce G. Knuth References to gemstones appear in many ancient writings. They may be ...
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3rd Century, Roman "Pointed" Diamond Ring. © The Trustees of the British Museum.

A History Of Diamond Cutting

This article gives an overview of the history of diamond cutting. For detailed descriptions of the different diamond cuts see ...
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6.79 Carat French-Cut Diamond, Angeled View.

Adamantine Luster

Adamantine is the term used to describe the luster exhibited by diamonds and gems with a Refractive Index of 1.9 - 2.5. The root word adamant ...
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Raymond Yard Moonstone Brooch and Earrings.

Adularescence

Adularescence is an optical phenomena often called the “moonstone” effect. The phenomenon is applied to feldspar, usually orthoclase that, when ...
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Art Nouveau Orthoclase Feldspar (Moonstone) Pendant.

Adularia

Adularia is a variety of orthoclase feldspar that is colorless to milky in appearance. It is mineralogically a potassium, aluminum, silicate feldspar found ...
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Banded Agate Cabochon in a Seed Pearl Frame.

Agate

Agate is a variety of chalcedony found in many different colors and degrees of translucency. There are several varieties of ...
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Aggregate

Aggregate in the geologic or gemologic sense of the word, is defined as a composition of various materials (usually mineralogical ...
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A contemporary shot of the Agra.

Agra Diamond

Like many historical diamonds, the Agra’s saga is a familiar combination of fact and legend, leaving the reader with the challenging ...
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Shah Jahan ca. 1620

Akbar Shah Diamond

Unfortunately, the history of famous diamonds is not without its list of casualties. In this category are those magnificent stones that somehow ...
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Alabaster

Alabaster Carving on Onyx Background. Alabaster is a name used for gypsum and calcite but has also been used to indicate selenite ...
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Alexandrite and Diamond Ring.

Alexandrite

Alexandrite is a variety of chrysoberyl with a distinct change of color when viewed in incandescent and fluorescent light. The ...
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Synthetic Alexandrite-Like Sapphire and Enamel Art Deco Ring.

Alexandrite-Like

 Alexandrite-like refers to the ability of a gem material to change colors when viewed under different light sources such as daylight and ...
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Edwardian_Sapphire_Diamond_Ring

Allochromatic

 The term allochromatic is used in reference to gem materials that derive their color from elements that are not an ...
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Alluvial Fan

Alluvial

Alluvial means 'deposited by water'. The word 'alluvial' is derived from the Latin word 'alluvius', from 'alluere', which means 'to ...
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Almandine Garnet Ring.

Almandine

These deep purplish-red garnets were often featured in Victorian Jewelry. When they are cut en cabochon they are referred to as "carbuncles." For more ...
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Wild Strawberry Brooch with Amazonite Leaves.

Amazonite

Amazonite, a variety of the microcline series of the feldspar group, gets its name from the Amazon River. A gridlike structure visible in ...
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Art Deco Amber Teardrop Earrings. Signed Day, Clark & Co.

Amber

In the forest primeval, a creature calls…Its echo is heard for millions of years.Frozen in time; the drama unfolds--A death ...
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Amethyst Brooch with Pearl Surround..

Amethyst

Amethyst is the most coveted member of the quartz family. It can be found in shades ranging from a very ...
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Ametrine Diamond and Opal Dragonfly Brooch. Photo Courtesy of Christie's.

Ametrine

Ametrine is a variety of quartz consisting of both amethyst and citrine with zones of both purple and yellow. Most ...
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Amorphous vs Crystalline structure

Amorphous

An amorphous substance is one that has no regular arrangement of atoms; it literally means "without form". Examples of materials ...
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Andalusite var. Chiastolite.

Andalusite

The name, Andalusite, is an homage to the city of Andalusia, Spain. Gem quality examples of this mineral species are ...
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Antique Demantoid Garnet Earrings.

Andradite

Andradite Garnet var. Demantoid ...
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Band

Anniversary Gifts

This anniversary gift list is a recent compilation that is recognized by the American Gem Trade Association, Jewelers of America, ...
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Apatite

Gems & Gemology: The Quarterly Journal of the Gemological Institute of AmericaApatiteSummer 1962, Cat’s-Eye Apatite, p. 315, 2pp.Summer 1963, Yellow Cat’s-Eye ...
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Aquamarine Ring.

Aquamarine

Aquamarine is the blue variety of the mineral beryl. Most natural aquamarine is a pale bluish green, which was the ...
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Aragonite.

Aragonite

Aragonite is a naturally occurring crystal form of calcium carbonate and is a precipitate from salt and freshwater conditions. One ...
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The Archduke Joseph Diamond

Archduke Joseph Diamond

This stone enjoys the distinction of being the twelfth largest “perfect” diamond in the world. Named for a military man of ...
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Arcot Diamonds Set in a Brooch.

Arcots

ARCOTS – A Pair of Diamonds These two exceptionally beautiful pear-shaped diamonds began their travels from the Nawab of Arcot ...
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Asscher-Cut Diamond Ring.

Asscher Cut

In 1902 the Dutch diamond cutter Joseph Asscher developed the cut that would carry his name on into the future ...
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Star Ruby, Diamond, Platinum Ring Exhibiting Asterism.

Asterism

Asterism is an optical phenomenon that results in the reflection of light rays on a gemstone, cut en cabochon, forming a ...
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Aventurescence in Goldstone.

Aventurescence

Aventurescence is a phenomenon in gemstones whereby glittering reflections of small inclusions of hematite or goethite in feldspar or fuchsite ...
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Aventurine

Aventurine Quartz Rough ...
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Azurite.

Azurite

Gems & Gemology: The Quarterly Journal of the Gemological Institute of America. Azurite: Fall 1960, Azurite and its Absorption Spectrum, p ...
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Azurmalachite Specimen. Photo: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0.

Azurmalachite

Sources Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 22-23. Schumann, Walter. Gemstones of the World, New ...
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Art Deco Baguette Diamond Ring.

Baguette Cut

The baguette cut represents an elongated, rectangular table cut. The modern version, as in the ring on the right, was (re)introduced ...
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Banjarmasin Diamond. Courtesy of the Rijksmuseum, The Netherlands.

Banjarmasin Diamond

One could rightfully call this stone the Rodney Dangerfield of diamonds. Almost from the moment of its discovery, this diamond has ...
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The Beau Sancy.

Beau Sancy

This diamond's name is taken from its first recorded French owner, Nicolas Harlay de Sancy, a fancier of fine gems who ...
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Benitoite.

Benitoite

Gems & Gemology: The Quarterly Journal of the Gemological Institute of America. Benitoite: Summer 1953, Benitoite, by Ehrmann, p. 317, 1p ...
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Morganite

Beryl

Beryl is a beryllium aluminum silicate that occurs in every color of the rainbow but is colorless in pure form; ...
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Jadeite Bi Earrings with Chinese Character Center.

Bi

 A bi (from Chinese) is jadeite discoid with a central hole. These doughnut-shaped gem disks are used for pendants, bracelets and earrings ...
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Doubling Zircon

Birefringence

Birefringence is the strength of double refraction as measured by computing the difference between the high and low indices of a ...
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Birthstones

The tradition of birthstones, or birthday stones, is a Polish 18th-century popularization1 of accumulated superstition and tradition which were ...
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Biwa Pearl and Diamond Brooch.

Biwa Pearl

Biwa pearls are a cultured pearl produced in a freshwater mussel native to Lake Biwa, Japan. Considered to be a non-nucleated pearl, they are ...
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Pearl Necklace

Bleach

Akoya Pearl Necklace.Akoya pearl bleaching is a common, but generally undisclosed treatment used to even out the color in white cultured pearls ...
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Tiffany & Co. Bloodstone Intaglio Signet Ring with a Coat of Arms Seal.

Bloodstone

Who on this world of ours his eyesIn Aries opens shall we be wiseIf always on his hand there liesA ...
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Bodycolor,cream

Body Color

Body color refers to a pearl's overall color. White, cream, pink and black are the most commonly seen body colors. The ...
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Boule

Split Boules of Flame Fusion Corundum.Photo by Morion Company. Boule refers to the rough form of synthetic corundum or spinel, produced through the flame ...
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Brilliance

Brilliance is a term used to quantify the brightness of a gemstone. Brightness, and therefore brilliance, are related to the surface ...
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Brilliant-Cut Diamond Ring.

Brilliant Cut

Diamonds as We Know Them When we think of a diamond, most of us will form an image in our ...
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Mid-Nineteenth Century Fuschia Design Diamond Brooch with en Tremblant Stems Suspending Detachable Briolette Cut Diamonds. Photo Courtesy of Christie's.

Briolette Cut

Edwardian Garland Motif Pendant Suspending a Briolette Cut Diamond. Briolettes are drop shaped, multi faceted stones. They are unique in ...
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2008 sketch of the Golden Fleece (of the Color Adornment) Showing the "French Blue" Diamond.

Brunswick Blue

To paraphrase Charles Dickens, this is a tale of two diamonds. Purportedly cut from the same stone that produced the Hope Diamond, ...
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Diamond Bruting Machine - Rounding 2 Diamonds by Grinding them Together as They Spin.

Bruting

Bruting is a process in diamond cutting that establishes the girdle outline. Once the height and width of the diamond are determined, it is ...
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Scottish Kilt Pin with Cairngorm

Cairngorm

Cairngorm is the name given to a citrine quartz variety with an amber or brown color traditionally mined in the Cairngorm Mountains in ...
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Conch Pearl Ring.

Calcareous Concretion

Calcareous concretions are pearl-like growths produced in mollusks that lack nacre. While still composed of calcite and aragonite, the crystals are much coarser. Some ...
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Calcite

Calcite

Sources Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 41-43. Schumann, Walter. Gemstones of the World, New ...
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Pinctada Margaritifera Shell. Image Courtesy of parels-ael.nl

Calcium Carbonate

Calcium carbonate is a primary component of the shells of marine mollusks and pearls. The outer shells of mollusks are ...
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Edwardian Rose Cut Diamond Natural Pearl Calibre Ruby Ring Circa 1900.

Calibré

Calibré refers to gemstones cut precisely to fit a specific design. Usually, calibré cut stones are rectangular or square but can be ...
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Carat

A unit of weight for gemstone materials. One carat equals 0.200 grams ...
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Carbon

Carbon is a chemical element on the periodic table. Carbon is the 15th most abundant element in the earth's crust ...
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Victorian Garnet and Diamond Pendant.

Carbuncle

A large almandine garnet that is cut en cabochon. These deep purplish-red garnets were popular in Victorian jewelry. Victorian Garnet and Diamond Pendant ...
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Carnelian Intaglio Ring.

Carnelian

Carnelian (or cornelian) is the translucent red variety of chalcedony which in its turn is a form of cryptocrystalline quartz. It's been known and used since ...
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Cat's Eye Chrysoberyl and Diamond Ring.

Cat’s-Eye

Cat's-Eye is an optical phenomenon (also known as chatoyancy) whereby light reflects back off a gemstone, cut en cabochon, as a single ...
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Giuliano Cave Pearl

Cave Pearls

Cave pearls are not actually pearls, they are a calcareous concretion occurring in subterranean limestone caves. While they bear a resemblance to pearls, ...
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Art Deco Chalcedony, Amethyst, Glass and Diamond Bracelet by Black Starr and Frost

Chalcedony

Chalcedony is cryptocrystalline quartz. It is semitransparent to opaque and, depending on its color, chalcedony is further divided into several varieties. History ...
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Color Change Sapphire.

Change of Color

 A phenomenon of some colored gemstones in which the gem material appears a different color in incandescent light than in daylight ...
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Chatham

Chatham, as used in gemological conversation, stands for a manufacturing technique of synthetic gemstones. The method incorporates crystallization of a ...
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Cat's Eye Chrysoberyl, Diamond, Platinum Ring Exhibiting Chatoyancy.

Chatoyancy

An optical phenomenon which appears as a bright band of light across certain gemstones that when cut as cabochons, reproduce ...
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Chlorastrolite.

Chlorastrolite

Chlorastrolite. Sources Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 49-50 ...
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Cat's Eye

Chrysoberyl

Chrysoberyl is among the most brilliant of gems and its hardness is only surpassed by diamonds and corundum. The name ...
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Tumbled Chrysocolla.

Chrysocolla

Chrysocolla is an intense blue-green to light blue variety of chalcedony. It can be translucent to semitransparent and is usually cut en cabochon. Tumbled ...
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Chrysoprase and Lapis Bypass Ring

Chrysoprase

Chrysoprase is the name reserved for bright green cryptocrystalline quartz. It is a subvariety of chalcedony and owes its beautiful green color to the ...
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French Japonesque Cinnabar, Diamond and Onyx Jabot Pin

Cinnabar

French Japonesque Cinnabar, Diamond and Onyx Jabot Pin.  Online Texts on Cinnabar Some Cinnabar Deposits in Western Nevada by Knopf ...
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Vintage Citrine Bracelet.

Citrine

Citrine is a yellow or golden variety of quartz, colored with iron. Natural citrine is relatively rare, occurring in Brazil, ...
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Clarity

A very included spessartite garnet. This stone has a very low clarity grade of I3. The grading of a gemstone ...
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Cleavage

DefinitionThe ability of a material to split along a certain plane or planes with weak atomic bonding. A crystal structure ...
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Minnie Palmer

Cleveland Diamond

If ever fate has lent a hand in determining the course of a diamond's story, it is this one. Just a ...
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Multi-Gemstone Necklace.

Colored Stone

Colored stones are all gemstones that are not a diamond. The term is used as a general catch-all for gemstones.Georgian Style ...
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Opal Doublet/Triplet

Composite Stone

Composite Stone - Triplet. Composite stones are gem simulants that are composed out of several materials. Doublets and triplets are good examples. Composite stones ...
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Belle Epoque Conch Pearl and Diamond Necklace.

Conch Pearls

A conch pearl is not technically a pearl at all, but a white or pink (sometimes brown or yellow), non-nacreous, product of ...
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Art Deco Black Mother-of-Pearl Cuff Links.

Conchiolin

 A dark organic substance secreted by some invertebrate animal life including coral polyps and pearl producing mollusks. Conchiolin is the ...
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Copal

Copal

Copal is a fossilized organic resin. This amorphous yellow to brownish material is often confused with amber, but amber is much ...
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Pair of Earrings Each with Four [[Coque de Perle]] (Nautilus Shell 'Pearls'); Bordered with Iron Pyrites Set in Silver. 1726-1775 © Trustees of the British Museum.

Coque de Perle

Coque de perle, from the French for 'pearl shell' was a Georgian faux pearl carved from the East Indian nautilus ...
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Art Deco Diamond and Coral Drop Earrings.

Coral

Coral is one of a very few organic gemstones. It consists of a mass of skeletons of tiny marine invertebrates ...
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Multi-Color Sapphire and Diamond Ring.

Corundum

DefinitionThe mineralogical name for Al2O3, the corundum family encompasses the gem varieties sapphire and ruby. It crystallizes in the trigonal structure and is ...
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Crown, Girdle, Pavilion

Crown-Gemstone

Crown, Girdle, Pavilion.The crown of a gemstone refers to the part above the girdle ...
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Early 20th Century Pin Centered with a Translucent Oval Cabochon Chrysoprase Chalcedony. Image Courtesy of Lang Antiques

Cryptocrystalline

Having crystals so small that individual crystals cannot be seen under ordinary optical microscope, but are detectable by effect under ...
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Crystalline

A crystalline material is a substance with a regular, repeating, 3-dimensional atomic structure. We divide crystalline materials into monocrystalline and ...
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Round Brilliant-Cut Cubic Zirconia.

Cubic Zirconia

Round Brilliant-Cut Cubic Zirconia. Cubic zirconia is a man-made material used to imitate diamond and other gemstones, commonly referred to as CZ. Cubic ...
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Culet

Culet

Culet. The tip of the pavilion is called the culet. Sometimes in the form of a facet, sometimes as a sharp point ...
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The Nine Most Important Cullinan Diamonds. Top Row: II, I and III. Bottom Row: VI, VIII, IV, V, VII and IX.

Cullinan Diamond

It was the late afternoon of January 25, 1905. Employees at the Premier Diamond Mine in the British African colony ...
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Antique Cushion-Cut Diamond Ring.

Cushion Cut

Cushion cut is a sexy and romantic name for a squarish ("cushionesque") antique brilliant-cut diamond, sometimes referred to as an ...
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Synthetic Ruby, Czochralski Boule.

Czochralski

Synthetic Ruby, Czochralski Boule. The Czochralski method, developed by Polish scientist Jan Czochralski, was a byproduct of his investigation into ...
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Darya-e-Noor Diamond.

Darya-ye-Noor Diamond

Darya-ye-Noor Diamond. Darya-ye-Noor, translating “river of light” or “sea of light”, is the product of an undocumented – but what ...
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Antique Demantoid Garnet Earrings.

Demantoid

At the end of the reign of Nicholas I, Emperor of Russia, and the beginning of the reign of Tsar ...
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Asscher-Cut Diamond Ring.

Diamond

Diamonds are valued for their incredible brilliance and hardness. Diamonds are chemically pure carbon, identical to the graphite used for ...
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6 Loose Diamonds in Different Cuts.

Diamond Cutting & Grading

Diamond CutsMain Article  Gems & Gemology: The Quarterly Journal of the Gemological Institute of America Diamond Cutting & Grading: Summer 1936, ...
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Transparent Rock Crystal Quartz Bead Necklace.

Diaphaneity

Diaphaneity is the general term to describe the transmittance of light through an object. The three typical classifications are transparency, translucency, and opacity ...
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Dichroism

The property of many doubly refractive colored gemstones of transmitting two different colors in two different vibration planes due to differences of selection absorption ...
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Dichroscope

A small gemological instrument that is used to detect pleochroism in a material. Using either a calcite crystal or polarizing ...
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Diffusion

Diffusion treatment is a treatment used to alter the color of a gemstone (mostly sapphires). Smaller atoms, usually beryllium, enter ...
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Grossular Diopside.

Diopside

Grossular Diopside. Photo Courtesy of Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 ...
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Synthetic Rutile Showing a High Amount of Dispersion. Image courtesy of Jeffrey Hunt.

Dispersion

Synthetic Rutile Showing a High Amount of Dispersion. Image Courtesy of Jeffrey HuntThe separation of white light into the component ...
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Zircon has a Very High Birefringence which is Clearly Visible in this Shot. The Back Facets Appear Doubled. Image courtesy of Jeffrey Hunt.

Double Refraction

The property of splitting a single beam of light into two polarized beams which pass through a crystal at different ...
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Doublet

Doublet

A composite gemstone consisting of two pieces of the same or different gem materials, or one gem material and a second of ...
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The Dresden Green Diamond in its Setting.

Dresden Green

The Dresden Green Diamond in its Setting. Labeled as the greatest example of a naturally green colored diamond, the Dresden Green ...
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Druse

Druse

A surface covered with small projecting crystals, usually lining the sides of a cavity ...
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Art Nouveau Ivory and Gold Mermaid Brooch.

Dull Luster

Dull luster describes the luster of Ivory. Japanese Shibayama Ivory Box with Dull Luster ...
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Durability

Durability refers to a quality of gemstones to withstand wear and tear in normal use. It depends on hardness (the ...
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French Straight Line Emerald Bracelet.

Emerald

Emerald is the green variety of the mineral beryl, owing its vibrant color to a trace amount of chromium and ...
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Emerald-Cut Diamond Ring

Emerald Cut

The Emerald Cut is a rectangular step cut design which means it has horizontal facets which differ in angles of ...
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Gem Quality Crystal.

Emeralds from Habachtal, Austria

Emeralds from Habachtal / Austria in Jewelry and arts by Nikolaus B.G. Lackner   IntroductionPicture of Trapeze Cut Habachtal Emerald Placed ...
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The Emperor Maximillian Diamond Weighing 39.55 Carats. Photo Courtesy of Christie's.

Emperor Maximilian & Maximilian Diamonds

Although these two diamonds are often spoken about in the same breath, no two stones could be more different – ...
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Sapphire Cabochon Ring.

En Cabochon

Imperial Jadeite and Diamond Art Deco-Style Ring.The phrase en cabochon (from French: knob) is the term applied to a gemstone ...
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Natural Amethyst and Heat Treated Amethyst-Gone-Citrine

Enhancement

Laser Drilled Diamond. The Visible Drill Channels are Not All Individual Channels, for the Most Part, They are Reflections.Image Courtesy ...
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Epidote Crystals.

Epidote

Epidote Crystals. Photo Courtesy of Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 ...
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Empress Eugenie (1853-1871)

Eugénie Diamond

Believed to be of Brazilian origin, this much-traveled diamond has not only changed hands many times, it’s also one of the few ...
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7.41 Carat European-Cut Diamond Drop Earrings

European Cut

Diamonds cut in the later 19th and early 20th-century cutting houses are called 'Old European Cuts', a term which indicates ...
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69.68 ct. Excelsior I, G-VS2. Photo Courtesy of Mauawad.com.

Excelsior Diamond

June 30, 1893, appeared to be just another day at the Jagersfontein Mine in South Africa until a worker, performing ...
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The Crown is Comprised of the Table, Main, Star and Girdle Facets.

Facet

Definition A facet is a flat, planar surface ground onto a gemstone or diamond. Facets can be produced in many shapes and sizes ...
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Slide 9 Map Western Minas Gerais State, Dashed Lines Showing the Approximate Region where Kimberlites and Associated Rocks Occur.

Fact or Fiction

Dr Don Hoover FGA, FGAA (Hon.) Presented to the Gemmological Seminar of the 61st Annual Federal Conference of the GAA, ...
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Coco Chanel Faux Pearl, Turquoise and Rhinestone Necklace.

Faux

Faux (from French: "false") is the name given to imitation jewelry, in particular to simulated pearls.Coco Chanel Faux Pearl, Turquoise and Rhinestone ...
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Feldspar var. Moonstone.

Feldspar

Feldspar var. Moonstone. Feldspar is a gem group that includes microcline, orthoclase, and plagioclase varieties. Each variety varies as to ...
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Glass Filled Ruby

Filling

Filling is a gemstone enhancement method which indicates a broad range of treatments. From simple oiling to resin impregnation to the filling ...
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Synthetic Rutile Showing a High Amount of Dispersion. Image courtesy of Jeffrey Hunt.

Fire

Synthetic Rutile Showing a High Amount of Dispersion. Image Courtesy of Jeffrey HuntA popular term used to describe the flashes ...
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Fire Agate

Fire Agate

Fire Agate is an iridescent brown form of chalcedony. Fire Agate ...
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A Second Typical Feature of Verneuil Corundum: Clouds of Small Gas Bubbles.

Flame Fusion

Flame fusion, discovered in 1902 by Auguste Verneuil, was the first successful process creating synthetic gemstones. Using powdered elements and high ...
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A Replica of the Florentine Diamond.

Florentine Diamond

Studying the history of this diamond is an exercise that will challenge even the most talented detective. Almost everything about this diamond’s ...
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Fluorescence

Fluorescence

The emission of visible light by a material, such as a diamond, when illuminated by ultra-violet light or X-radiation. A ...
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Borax

Flux

Literally meaning "flow", a flux is a liquid in which some solid substances melt at a lower temperature than their ...
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Pyrite

Fool’s Gold

Fool's gold is the popular name for pyrite. Pyrite looks like gold but is hard and brittle and lacks the malleability of gold. Fool's Gold aka ...
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Conchoidal

Fracture

A break or chip, caused by stress, that is in any direction other than parallel to the planes of atoms ...
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6.79 Carat French-Cut Diamond, Top View.

French Cut

Art Deco French-Cut Diamond Straightline Bracelet.The term "French Cut" does not refer to the country of origin, rather It refers ...
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G&G Articles on Famous Diamonds

More Information Gems & Gemology: The Quarterly Journal of the Gemological Institute of America. G&G Article Index:  Famous Diamonds Below please ...
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Almandine Garnet Ring.

Garnet

The term garnet applies to a group of minerals with six main varieties. The varieties differ in chemical composition and ...
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Typical, Perfectly Spherical Bubble in Paste Resembling the © Sign. Photo by Tim Spauwen.

Gas Bubble

Gas bubbles are the rounded bubbles seen in glass resulting from trapped gasses during the manufacturing process. It is sometimes necessary to ...
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Vintage Black Opal and Diamond Ring Exhibiting Play-of-Color.

Gem Phenomena

Gem phenomena, or optical phenomena, are the observable characteristics of gemstones, such as asterism, play-of-color and chatoyancy. Phenomena are usually a result of light interacting ...
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Gem-A

Gem-A is the short name for The Gemmological Association of Great Britain. This is the oldest and most prestigious gemmological educator ...
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Gemology

Gemstones From Agate to Zircon CategorieS Gemstone InformationGemology Gemology Terms From Adularescense to ZoistiteFamous Diamonds The Biggest and Best Diamonds ...
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Multi-Gemstone Necklace.

Gemstone

A gemstone is a stone of organic or inorganic - such as mineral - nature. The difference between a mineral ...
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A Foil Backed Colorless Quartz Cabochon.

Gemstone Surface Enhancements

Surface Enhancements Gemstone surface treatments are techniques that are applied to the surface of gemstones and diamonds in order to enhance ...
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Geuda Sapphire, Sri Lanka.

Geuda

The Sri Lankan geuda sapphire is a pale, translucent, and, until the discovery of heat treatments, useless variety of sapphire ...
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Gadolinium Gallium Garnet aka GGG

GGG

Gadolinium Gallium Garnet. A synthetic gemstone used as an early diamond substitute. GGG is manufactured by the Czochralski method and ...
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Arts & Crafts Moonstone Bracelet Exhibiting Girasol.

Girasol

Any gem variety that exhibits a floating, milky sheen that moves about as the stone is turned or as the ...
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Crown, Girdle, Pavilion

Girdle

Crown, Girdle, PavilionThe band on a faceted stone, around the widest circumference, which creates the separation of the crown and ...
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Conchoidal

Glass

Most glass is a man-made material sometimes used to simulate a gemstone. In that case, it's called paste. There are also three ...
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Golden Jubilee Diamond.

Golden Jubilee

If you record size as the number one trait in judging the importance of a diamond then this stone would top your ...
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Art Deco Gota De Aceita Emerald Brooch.

Gota de Aceita

In addition to the streamlined geometric styling, fine Art Deco jewels of the 1920s-30s are noted for their superior gemstones and here we have ...
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Serpentine Paten with Gold Inlay Surrounded by Gems in Gold 1st Century BC. In the Collection of the Louvre, Paris.

Greasy Luster

Greasy is the term used for the surface reflection on materials as seen on Serpentine. Serpentine Paten with Gold Inlay ...
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Early Drawing of the Great Mogul Diamond.

Great Mogul Diamond

This is the kind of story that would make a great Indiana Jones movie – solving the mystery of the ...
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Tsavorite Garnet Ring.

Grossular

Tsavorite 1967 - Discovered in Northern Tanzania close to the Kenyan border by Campbell R. Bridges. Mining the deposit wasn't ...
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Gübelin Maker's Mark

Gübelin

Lucerne, Switzerland, 1854, Jakob Josef Mauritz Breitschmid opens a watchmaker's shop. Jakob's apprentice, Eduard Jakob Gübelin, marries his daughter Bertha ...
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Shell Cameo Habille with Earring, Necklace and Diadem, Set with Diamonds. Circa 1920's.

Habille

A habillé is a cameo in which jewelry, earrings, for instance, is incorporated in the portrait. These highly collectible cameos came in ...
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Moh's Scale of Hardness. Photo Courtesy of the National Park Service.

Hardness

Hardness in jewelry terms (and gemology) means the ability of a subject to withstand abrasion by another subject. The most ...
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Hardstone Cameo Depicting Athena Wearing a Helmet with a Live Serpent on Top and a Secondary Visage on the Visor. Her Chest Armor Displays the Aegis of Zeus.

Hardstone

Hardstone Cameo Brooch made in Sweden. Hardstone is a term used loosely to refer to any hard gem material used ...
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Warren Hastings

Hastings Diamond

If ever there was a famous diamond named for a certified scoundrel, it’s the Hastings Diamond. Using this gem as a tool ...
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Swedish Heart-Shaped Diamond Ring.

Heart Shape

Heart-Shaped Diamonds.Main Article   ...
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Halo (Stress Fracture) in a Sapphire Indicating Possible Heat Treatment.

Heat Treatment

Introduction Gemstones are colored because certain wavelengths of the visible spectrum of electromagnetic radiation get absorbed while other wavelengths are transmitted. Which ...
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Heishi

Heishi jewelry is created by Santo Domingo and San Felipe Pueblo Indians from New-Mexico in the south-west of the USA ...
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These Antique Style Hematite Earrings are a Perfect Example of Metallic Luster.

Hematite

Hematite derives its name from the Greek word haema for blood. Thinly sliced hematite is a reddish color and, when rubbed against ...
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Hiddenite Parent Géry - Own work

Hiddenite

Hiddenite is the strongly pleochroic, bright green variety of spodumene. First discovered in North Caroline by W. E. Hidden in 1879. Sources ...
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Portrait of Queen Wilhelmina (1898)

Holland Diamond (Stuart)

This is the story of a diamond whose beginnings and early history are unknown, a casualty of lost or poor documentation. It ...
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Jade Hololith Ring. Image Courtesy of Christie's.

Hololith Ring

A hololith ring is a ring which is cut from a single, solid mineral. Many jade and chalcedony rings are cut this way. Jade Hololith Ring.Image Courtesy ...
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The Hope diamond. Image Courtesy of The Smithsonian Institute.

Hope Diamond

Thievery, royalty, revolution, gambling, eccentricity, mystery and curses are all part of the spectacular and storied past that is the ...
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Lalique Horn Comb. Photo Courtesy of Christie's.

Horn

Horn, commonly used in buckles, brooches, combs and hair ornaments was usually ox-horn, although it could be from any animal. With ...
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Hornbill Jewelry Suite.

Hornbill Ivory

In the fall of 2009 Stone Group Labs received an unusual item for identification. It turned out to be manufactured ...
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Horneblende.

Hornblende

Hornblende is a series of minerals, not a mineral in its own right. By composition, it is an iron-magnesium silicate that ...
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Hortensia Diamond, 20.53 Carats, Pink.

Hortensia Diamond

It seems each famous diamond has some kind of mystery attached to it, usually involving the location of its discovery, the identity ...
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HPHT Diamond Diagram.

HPHT

HPHT treatment stands for high pressure - high-temperature treatment. This method of diamond enhancement, invented in the late 1960's, started to be applied commercially ...
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Hydrogrossular garnet with ruby and diamond. Bombé design Signed Webb for David Webb. Photo courtesy of Christie's.

Hydrogrossular

A polycrystalline mineral in the garnet group that occurs in a green or pink color, sometimes intergrown with idocrase. Bright green samples are sometimes used ...
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Almandine Garnet Necklace.

Idiochromatic

The term idiochromatic is used in referral to gem materials that derive their color from elements that are an essential ...
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Vesuvianite aka Idocrase.

Idocrase

Vesuvianite aka Idocrase.Photo Courtesy of Rob Lavinsky, iRocks.com Idocrase is mineral species known as Vesuvianite and has several varieties. Sometimes ...
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Idols-Eye Diamond.

Idol’s Eye Diamond

Like many of its contemporaries, the Idol’s Eye diamond possesses an early history that combines a rich mixture of legend, myth, mystery, ...
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Vauxhall Paste Ring. Circa 17th Century. Photo Courtesy of the Museum of London.

Imitation

Paste Used to Imitate Yellow Natural Gemstones in Costume Jewelry.An imitation is an object or gemstone which is used to ...
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A Slender, Double Refractive, Crystal of Unknown Composition Causes a Beautiful Image When it's Host, a Garnet, is Placed in Between Crossed Polars. Image by Tim Spauwen.

Inclusion

Inclusions are internal features within a gemstone, often small enough to require a microscope for viewing. This term usually refers ...
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Victorian Onyx Intaglio Ring.

Intaglio

Intaglio is a technique which dates back to antiquity and is still in use at present. Patterns, designs or - ...
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Cordierite var Iolite

Iolite

Etymology The name, iolite, originates from the Greek word “iodes” meaning violet. It is often found under the misleading name ...
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Iridescence Causes Beautiful Colors on Ammolites.

Iridescence

The rainbow effect inside or on the surface of a material produced by light interference or diffraction from thin films ...
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n 1904 William Crookes, a well known physisist discovers that diamonds turn green upon exposure to radium. (TIm)

Irradiation

In 1904 William Crookes, a well known physicist discovers that diamonds turn green upon exposure to radium. The diamonds stayed radioactive and ...
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Cartier Ivory Flower Brooch, c.1950. Photo Courtesy of Sotheby's

Ivory

Historically, this organic gem material referred to as Ivory came only from elephant tusks. Since elephants have become a protected ...
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Carved Natural Jade Pendant.

Jade

Jade is in the gemstone family that includes both Jadeite and Nephrite. The term Jade is still often interchanged with jadeite and nephrite ...
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Jadeite Ear Clips

Jadeite

Jadeite is a silicate containing sodium and aluminum. Jadeite occurs in a very wide range of colors, translucencies and textures ...
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Victorian Scottish Agate and Jasper Brooch.

Jasper

Scottish Jasper Brooch. Jasper is a member of the chalcedony family of gemstones. The name is of Greek derivation meaning spotted stone ...
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Victorian Faceted Jet Locket-Necklace Worn for Mourning.

Jet

A Jet Box with a Pietra Dura Inlay. Jet is a type of brown coal used since the Stone Age ...
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Kashmir Sapphire and Diamond Ring

Kashmir Sapphire

Kashmir Sapphire and Diamond Ring. Undoubtedly, the rarest and most beautiful of all sapphires are the legendary Kashmir. As befitting such otherworldly ...
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Kazanjian Red Diamond. ©Tino Hammid, Los Angeles

Kazanjian Red

Kazanjian Red Diamond.©Tino Hammid, Los AngelesThis stone belongs to an extremely small – and select - group of diamonds. It ...
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The Koh-i-noor Set in the Coronation Crown for Queen Mary (Wife of King George VI) Mother of Queen Elizabeth II. (Reuters Photo)

Koh-i-Noor Diamond

The Fabled Koh-i-Noor Diamond Like other famous gems, the Koh-i-Noor diamond has its share of mystery, intrigue, and curses attached to its ...
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Retro 70 Carat Kunzite Ring with Bold Gold Mount.

Kunzite

Kunzite and Diamond Ring. Kunzite, a variety of spodumene, was named for George F. Kunz who was the first to describe ...
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Large Scale Synthetic Star Ruby and Platinum Diamond Ring

Laboratory Grown

Gemstones that are produced by man are generally termed "laboratory grown". These can be synthetics or other inorganic minerals that have no ...
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Egyptian Revival, Victorian Scarab Brooch, c.1870.

Labradorescence

Labradorescence is a play-of-color gem phenomenon that occurs in gem quality labradorite. The phenomenon results from reflection of light from the layers of thin ...
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Arts and Crafts Labradorite Brooch.

Labradorite

Labradorite is a mineral species of the plagioclase series of the feldspar group. Egyptian Revival, Victorian Scarab Brooch, c.1870 ...
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Hardstone Cameo Brooch made in Sweden.

Lapidary

A lapidary is a person who cuts or carves and polishes gemstones, stone, minerals and other hard materials excluding diamonds. Lapidaries render decorative ...
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Lapis Lazuli Pendant.

Lapis Lazuli

Lapis lazuli is a rock aggregate made up from - predominantly - the minerals lazurite, sodalite, nosalite and hauyne. It ...
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Laser

Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. A powerful, coherent, straight-line beam of light, very ...
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Laser Drilled Diamond.

Laser Drilling

Laser Drilled Diamond. The Drill Channels you See are Not All Individual Channels, for the Most Part, They are Reflections.Image ...
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Louis II de Bourbon aka le Grand Condé

Le Grand Condé

Louis II de Bourbon - aka le Grand Condé If there was an award for the most gaps in a ...
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Art Deco Lozenge Shape Diamond and Sapphire Ring.

Lozenge Shape

A lozenge-shaped diamond is one that is rhomboid in outline. This geometric outline is also known as "diamond" shaped, but ...
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Pearl Luster.

Luster

The quality and quantity of light reflected from the surface of a gemstone. Luster depends on the refractive index and the polish or surface condition ...
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Natural Diamond Macle, by Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Macle

Diamond Macle.Macle is a gemological term referring to triangular shaped twinned crystals of diamond rough. Macles are usually quite flat but are ...
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Dionysus Rendered in Malachite.

Malachite

Malachite is green stone with irregular bands of lighter and darker green. The name malachite comes from the Greek word malache which ...
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Mallorca Pearl.

Mallorca Pearls

Majorica is a brand name of a high-quality pearl simulants produced on the Spanish island of Majorica at the Majorica S.A. company ...
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Mantle

Mantle is the tissue in a mollusk where pearls are formed. In the culturing process for pearls, a bit of ...
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Black Enamel and Marcasite Pendant Watch

Marcasite

Marcasite is an iron sulfide mineral with an orthorhombic crystal structure. It is very brittle and unsuitable for jewelry. What ...
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Marquise-Cut Diamond.

Marquise Cut

The Marquise Cut (a.k.a. the Navette Cut after the Latin 'navalis', meaning boat-shaped) can be traced back to Paris around ...
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Dioptase in Matrix.

Matrix

In mineralogy, the term matrix stands for the host rock in which a mineral is contained. Here you can see the mineral ...
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The Mazarin I: the Sancy

Mazarins

This diamond story is an unusual one. In most instances, a name is attached to one or perhaps two diamonds but in ...
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Meershaum Cigarette Holder in a Fitted Case.

Meershaum

Meershaum is a smooth porous clay-like material that is light enough to float. Its whitish color makes it similar in ...
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Pink, Yellow and Light Brown Diamond Melée. Photo Courtesy of Bonhams.

Melée

The term melée is used to indicate very small cut stones, usually used as side stones around a bigger center ...
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These Antique Style Hematite Earrings are a Perfect Example of Metallic Luster.

Metallic Luster

Metallic Luster on Hematite. Metallic luster is the highest luster. Found on gems with a refractive index of 2.5 or ...
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Orange Fire Opal and Diamond Ring.

Mexican Fire Opal

Fire opal refers to the variety of transparent red, orange or orangy-red opal usually lacking play-of-color. Fire opal is cut en cabochon as ...
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Wild Strawberry Brooch with Amazonite Leaves.

Microcline

Amazonite in Albite Specimen. Photo: Rob Lavinsky, iRocks.com Microcline is a mineral series in the feldspar group. Amazonite is a light green ...
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Microcrystalline

Materials consisting of aggregated crystals are termed polycrystalline and if individual crystals can be seen only under magnification, the term ...
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Mikimoto, Kokichi

K. Mikimoto 1858-1954 Kokichi Mikimoto was born in Toba, Japan on January 25, 1858. Born of humble beginnings he was ...
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A 9.39 carat Cat's Eye Chrysoberyl is the Star of this Vintage Style Ring.

Milk and Honey Effect

The finest example of chatoyancy or “cat's-eye” is that displayed by the gemstone chrysoberyl. The most desirable Chrysoberyl is slightly greenish ...
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Mineral

A mineral is any naturally occurring inorganic solid created by a geological process that has a specific chemical composition, a ...
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Mirror of Portugal

Owners of this stone ranged from the tenacious to the hapless, the romantic to the cunning. This diamond helped persuade a Queen ...
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Moh's Scale of Hardness. Photo Courtesy of the National Park Service.

Moh’s Scale

Moh's scale is a relative hardness scale for minerals rating them from 1 to 10. The values are not proportional ...
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Moldavite from Besednice, Bohemia.

Moldavite

Moldavite is formed from melted rock resulting from a meteorite strike. The surface of these small specimens can be rippled ...
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Pinctada Margaritifera.

Mollusk

A mollusk is an invertebrate animal that is the source of all pearls. The mollusks that are important in jewelry ...
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Monoclinic

A low symmetry crystal system described by three axes, all unequal in length, two of which intersect at oblique angles ...
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Monocrystalline

Monocrystalline materials are substances with a regular, repeating atomic structure that are composed of a single crystal.The crystal shape is ...
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Art Nouveau Montana Sapphire and Pearl Pin.

Montana Sapphire

Tiffany Iris Corsage Brooch Set With Montanna Sapphires. © The Walters Art Museum. While most are familiar with the exotic ...
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Raymond Yard Moonstone Brooch and Earrings.

Moonstone

Moonstone is a variety of orthoclase feldspar, which is a sodium aluminum silicate. Moonstones can occur colorless, blue-white, white, and ...
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Mosaics in Jewelry

...There were couches of gold and silver on a mosaic pavement of porphyry, marble, mother-of-pearl and other costly stones.2 ...
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Moss Agate Ring by Allsopp Brothers.

Moss Agate

Early 20th Century Moss Agate Match Safe. Moss agate is a translucent chalcedony with green moss-like inclusions, usually hornblende. When the hornblende oxidizes, the color ...
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Exquisite Carved Mother of Pearl Cameo Pendant.

Mother-of-Pearl

Mother-of-pearl a nacreous, lustrous, iridescent lining of the shell of a mollusk that can be carved and cut for jewelry ...
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Mounting on Moor

"Mounting on moor" refers to the tinting of diamonds on the pavilion to create a more uniform color and to hide dark ...
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Around the Same Time Diamond Cutting Began in Europe the Indians Started Fashioning Diamonds. Who Influenced Who Here Isn't Clear but it is a Fact that the Designs Produced Differ a Lot From Each Other. The Best Known Indian Cut is the Mughal Cut, Accurately Described by J.B. Tavernier in his Book 'Six Voyages'.

Mughal Cut

Around the Same Time, Diamond Cutting Began in Europe the Indians Started Fashioning Diamonds. Who Influenced Who Here Isn't Clear ...
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Pinctada Margaritifera Shell. Image Courtesy of parels-ael.nl

Nacre

Pinctada margaritifera Shell. Image Courtesy of parels-ael.nl Nacre is the iridescent substance formed from the crystallization of calcium carbonate as aragonite, bound by conchiolin, which composes ...
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1,109-Carat Diamond, Lesedi La Rona, from the Lucara Mine, Botswana. Photo Courtesy of the New York Times.

Naif

A Naif is the outer surface of an unpolished and uncut diamond. When cutting a diamond a small bit of this ...
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A Side View 13a, Top View 13b, and Bottom View 13c of the Nassak Diamond as of 1904

Nassak

This particular stone could be the reason for the cliché “diamond in the rough.” During its early history, this stone ...
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Trigons on the Face of a Natural Diamond. Photo Courtesy of Gump Stump, Wikipedia.

Natural

A natural is a bit of the naif or outer skin of a diamond that remains after cutting and polishing. A natural on ...
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Victorian Navette Shaped Pearl and Diamond Ring.

Navette

Navette is another term to describe a marquise shaped gemstone or jewelry contour. Pointed at both ends with equally curved sides, the ...
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Sulka Nephrite Jade and Sapphire Cufflinks

Nephrite

Nephrite is a magnesium and calcium silicate with an interlocking fibrous structure that gives it extreme toughness. It is a ...
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Nicolo

Egyptian Nicolo Intaglio, Second Century AD.The Metropolitan Museum of Art. Nicolo is a cameo or intaglio that is carved in onyx in such a way that ...
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Conchoidal

Obsidian

Obsidian. Obsidian is a naturally occurring glass of volcanic origin, having an amorphous structure due to rapid cooling. It can ...
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Cedar Oil for Emerald Enhancement - Before and After.

Oiling

Oiling is a gemstone treatment typically used for emerald and other gems with cracks that extend to their surface. Applying oil, with a refractive ...
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Oligoclase Locality: Hawk Mine.

Oligoclase

Oligoclase is a mineral species of the plagioclase series of the feldspar group ...
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Victorian Onyx & Gold Mourning Necklace.

Onyx

Onyx is a variety of cryptocrystalline silicon dioxide or chalcedony. It is banded with contrasting colors making it an excellent ...
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Victorian Opal & Seed Pearl Pendant.

Opal

Opal is a hydrous variety of silicon dioxide. It is unlike other minerals because it is not crystalline! Opal is ...
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Mid-Century Opal Bracelet.

Opalescence

Milky or pearly appearance of some common opal. The term opalescence is also used to describe a shimmering milky-white or ...
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Opaline Glass Buttons c.18th Century. ©Victoria & Albert Museum.

Opaline Glass

Opaline glass was a gem imitation with a milky white to blue appearance generally cut en cabochon a popular daytime "gem" in ...
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Edwardian Opaque Turquoise and Diamond Pendant.

Opaque

Material that allows no light to be transmitted, even through thin edges. Opaque Red Coral and Diamond Pendant ...
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Opus Sectile (Marble Floor Inlay) from the Hadrian's Villa (Piccole Terme) Near Tivoli in Italy.

Opus Sectile

Opus Sectile is a mosaic style where slabs of stone are shaped and fitted together as a jigsaw puzzle. It ...
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Sea of Cortez Pearls, Mabes and Keshi from the “Rainbow Lipped Pearl Oyster” Pteria Sterna Exhibiting Orient. Photo Courtesy of The Sea of Cortez Pearl Blog.

Orient

Orient is the quality in a pearl in which rainbow-like colors appear to flow across a pearl's surface. This is a rarely ...
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The Orlov diamond in the Russian Imperial Sceptre Image courtesy of Elkan Weinberg.

Orlov Diamond

Perhaps there is no famous diamond with a more disputed history than that of the Orlov. Through the passage of ...
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Victorian Cat's-Eye Orthoclase Feldspar and Diamond Earrings.

Orthoclase

Orthoclase is a mineral series in the feldspar group. Moonstone Art Nouveau Orthoclase Feldspar (Moonstone) Pendant. Sources Gem Reference Guide, Los Angeles: ...
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Oval Fancy Deep Brownish Yellowish Orange. Diamond with Two Pair of Marquise-Cut Side Stones.

Oval Shape

Oval Diamond Three Stone Ring.Main Article   ...
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Tahitian Pearl with Greenish-Silver Overtone.

Overtone

Overtone is a quality in pearls in which one or two colors overlie the pearl's body color. Not seen in ...
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Paraiba Tourmaline Platinum and Diamond Earrings

Paraíba

Paraiba Tourmaline and Diamond Ring and Earrings.Photo Courtesy of Christie's. Paraiba is a tourmaline variety noted for its neon blue and green ...
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Antique French Enamel and Paste Silver Gilt Necklace.

Paste

Example of a Paste Sapphire Imitation. Notice the Rounded Facet Edges Which Tell Us the Stone Wasn't Cut, but Cast ...
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Vauxhall Paste Ring. Circa 17th Century. Photo Courtesy of the Museum of London.

Paste Jewelry

Paste jewelry is costume jewelry, mainly set with colored and/or colorless glass. During the eighteenth century with the vogue for faceted gems and diamonds, the demand ...
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Crown, Girdle, Pavilion

Pavilion

Crown, Girdle, Pavilion.The pavilion is the part of a gemstone below the girdle ...
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Pear-Shaped Diamond.

Pear Shape

Pear-shape refers to the shape of a faceted gemstone that comes to a point at one end and is rounded at the opposite ...
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Victorian Natural Pearl and Diamond Necklace

Pearl

Pearls are organic gems, produced in pearl oysters. Pearl oysters are not edible, and edible oysters do not produce gem ...
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Mikimoto Cultured Pearl Necklace Exhibiting Excellent Luster.

Pearl Luster

Pearl Luster is defined by the sharpness and brightness of reflections as seen on the surface of a pearl. The Gemological ...
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Akoya Pearl Necklace.

Pearl Types

All pearls originate in mollusks (mollusca), whether natural or cultured. Mollusks are a phylum of invertebrate animals that includes oysters, clams, mussels, ...
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Mid-Century Angel Skin Coral Necklace, Earrings and Ring.

Peau d’Ange

Peau d'ange (from French: angels skin) is a color description mainly applied to corals. It is a bleached to deep rosa color ...
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Louis-Jean Marie de Bourbon, (16 November, 1725 – 4 March, 1793)

Penthièvre

It is a diamond not as well known as its contemporaries. It is somewhat of an anomaly, for through its rich French ...
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Antique Peridot Pendant

Peridot

Peridot is the gem variety of the mineral chrysolite or olivine. It is a silicate of iron and magnesium found ...
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Petrified Tree in Petrified Forest National Park, USA. Image taken by Daniel Schwen on Sept 4th, 2004.

Petrified Wood

Petrified Wood is is wood that has been replaced by chalcedony aka silicified wood. In looks, it is very similar to patterned ...
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George Pigot (4 March 1719 – 11 May 1777)

Pigot Diamond

With apologies to Charles Dickens, this diamond’s story could be entitled the “Tale of Two Diamonds” for its history diverges ...
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Tortoiseshell Pique Pin.

Pique

Pique is a technique in which gold or silver is inlaid in tortoiseshell and sometimes ivory or mother-of-pearl. Another meaning is the French word for an inclusion in a diamond. Victorian Pique Brooch ...
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Arts and Crafts Labradorite Brooch.

Plagioclase

Plagioclase is a sub-series of the feldspar group. Labradorite Oligoclase Egyptian Revival, Victorian Labradorite Scarab Brooch, c.1870. Sources Gem Reference Guide, Los ...
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Bakelite.

Plastic

Plastics are man-made substances used in jewelry to imitate natural gem materials. Early plastics were organically derived, like the combination ...
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Vintage Black Opal and Diamond Ring Exhibiting Play-of-Color.

Play-of-Color

Black Opal, Diamond, Platinum Ring Exhibiting Play-of-Color.Play-of-color is the name for the phenomena in opal that produces the changing colors that seem ...
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Green Tourmaline and Diamond Halo Ring. The Tourmaline Color is a More Yellow Green from this Crystal Direction - Exhibiting Pleochroism.

Pleochroism

The property of most doubly refractive colored minerals of exhibiting either two or three different colors when viewed in different ...
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3rd Century, Roman "Pointed" Diamond Ring. © The Trustees of the British Museum.

Point Cut

Natural PointsA Natural Octahedronby Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 Diamonds crystallize in various forms of which the octahedral and dodecahedral ...
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Polycrystalline

Polycrystalline substances are minerals whose outer shape is not recognized as a clear crystalline form. The crystalline form can only ...
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Porous

Materials containing many small pores and spaces which may absorb fluids. Permeable to liquids; those crystalline and cryptocrystalline aggregates which permit the entrance of ...
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Prase

Prase

A leek green colored cryptocrystalline quartz aggregate with actinolite inclusions. Usually darker and less saturated than chrysoprase. In Greek the word Prason means leek, hence the name ...
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Prasiolite

Prasiolite is the green variety of Quartz. The material is extremely rare in nature and is only found in a handful ...
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Princess Cut

Being one of the more modern diamond cuts the Princess Cut is often indicated as being a square brilliant but this is ...
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Pyrite

Pyrite

Pyrite is an opaque yellow mineral with a metallic luster. Its cubic crystal system is evident in its outward appearance and specimens are ...
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Victorian Bohemian Garnet Earrings.

Pyrope

For over 600 years, the so-called 'Bohemian Garnets' from the Czech Republic amass the bulk of pyropes used in jewellery ...
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Quahog Pearl.

Quahog

A quahog is a bivalve clam native to the eastern seaboard of the United States. Used mostly as a food ...
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Quartz

Quartz is a commonly occurring variety of silicon dioxide. It often crystallizes into well-formed hexagonal prisms. Quartz occurs in many ...
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Queen of Holland Diamond. Photo Courtesy of Mouawad.

Queen of Holland

As diamonds go this one is pretty impressive, not only because of its size but because of its renowned quality ...
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Radiant-Cut Diamond.

Radiant Cut

Radiant-Cut Diamond.Main Article   ...
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Refraction Diagram.

Refraction

The change in the direction and speed of light as it passes from one medium into another of different optical ...
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Portable Refractometer.

Refractive Index

The ratio of the speed of light in air to its speed its speed in a substance. The ratio indicates ...
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Refractometer.

Refractometer

A gemological instrument which works on the principal of total internal reflection and which is used to measure the refractive index of gemstones ...
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Regent Diamond.

Regent Diamond

This magnificent gem has generated enough fodder to churn out a series of pulp fiction novels. Its travel through history is intertwined ...
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Art Deco Amber Teardrop Earrings by Day, Clark & Co. (Detail)

Resinous Luster

Resinous luster is that of a substance formed from resin. Example: Amber. Art Deco Amber Teardrop Earrings. Signed Day, Clark & ...
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French Antique Silver, Enamel and Paste Necklace

Rhinestone

Rhinestone is the name given to rock crystal which is faceted to imitate diamond. It is also a name for ...
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Rhodocrosite

Rhodochrosite

Rhodochrosite is a manganese carbonate mineral with a transparent to translucent rose-pink color with undulating bands of white, gray or ...
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Rhodonite

Rhodonite

Rhodonite is a translucent to opaque pink to reddish color gemstone with patches or veins of black throughout. Usually cut en cabochon or drilled ...
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Serpentinite

Rock

Rocks are an aggregate of minerals bonded and textured by the processes under which they formed. Because rocks are an aggregate with no particular ...
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French Frosted Rock Crystal Quartz and Diamond Pin

Rock Crystal

Natural Color-Change Sapphire, Rock Crystal and Diamond Pendant. The Greek word krystallos meaning "ice", provides the basis for the origin of the ...
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Georgian Floral Motif Diamond Engagement Ring.

Rose Cut

Rose-Cut Diamonds: Their Beauty and Allure Early "diamond cuts" were essentially diamonds altered with only minor changes and a light polishing before ...
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Rose Quartz Ring

Rose Quartz

Rose quartz gets its name from its rosy pink color. Because of its massive turbid crackled nature rose quartz is ...
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5 Petal Rosette Composed of Diamonds Cut to Form this Shape.

Rosettes

Rosettes are floral depictions built up out of several diamonds. They were used to make the most out of small ...
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No-Heat Ruby Platinum Diamond Ring

Ruby

Ruby is the red variety of sapphire or the mineral corundum. When corundum occurs in any color, other then red, ...
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Sancy Diamond Part of the Crown Jewels of France on Display at the Louvre.

Sancy Diamond

Sancy Diamond - Part of the Crown Jewels of France on Display at the Louvre.Diamonds tend to be described in such ...
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Edwardian_Sapphire_Diamond_Ring

Sapphire

Sapphire is a variety of the mineral corundum that occurs in spectacular colors with great durability and stability. When corundum ...
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Tiffany and Co. Sard Cufflinks.

Sard

Sard is a translucent to semi-transparent variety of chalcedony. The colors are similar to carnelian but they are darker and less ...
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Victorian Sardonyx Cameo Drop Earrings.

Sardonyx

Sardonyx is a brown and white banded variety of onyx primarily used in glyptography. Antique Victorian Sardonyx Seal Fob. SourcesGem Reference Guide, Los ...
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Allalin Glacier, Saas Valley, Zermatt-Saas Fee, Wallis, Switzerland

Saussurite

Saussurite is a rock formed from green zoisite in combination with epidote, white feldspar and other minerals ...
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Victorian Egyptian Revival Scarab Ring.

Scarab

A scarab is a beetle and was a recurring motif in Ancient Egypt. Ancient, as well as contemporary renditions in ...
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Round Brilliant-Cut Exhibiting Scintillation.

Scintillation

Scintillation is the term that describes the flashes of light reflected off the facets of a gemstone as it moves. Victorian Cluster Ring with ...
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Victorian Seed Pearl and Diamond Heart Pin - Pendant.

Seed Pearl

Seed pearls are very small; less than a one-quarter grain in weight, smaller than 2mm in size and off-round in shape. Historically they occurred ...
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Mid-Century Heart-Shaped Amethyst Ring.

Semi-Precious

Semi-precious is a term used to describe any gemstones that are not diamond, ruby, sapphire or emerald. Generally, the term is used to refer to ...
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Serpentine Paten with Gold Inlay Surrounded by Gems in Gold 1st Century BC. In the Collection of the Louvre, Paris.

Serpentine

Serpentine Paten with Gold Inlay Surrounded by Gems in Gold 1st Century BC. In the Collection of the Louvre, Paris ...
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A Stamp (From the Former Soviet Union) Depicting the Shah Diamond.

Shah Diamond

Imagine a diamond where the reader is not faced with the challenge of trying to separate fact from fiction when researching ...
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Shah Jahan Diamond. Photo Courtesy of The Metropolitan Museum of Art. Resides in the al-Sabah Collection, Dar al-Athar al-Islamiyyah, Kuwait.

Shah Jahan Table-Cut

By any gemological standard, the Shah Jahan Table-Cut Diamond is one impressive stone. Like many of its contemporaries, this diamond has gone ...
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Shale

Shale

A fissile (easy to split) sedimentary silicate-rich rock with particles mostly in the silt and clay size. The color is ...
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Victorian Shell Cameo Depicting Archangel Michael Slaying Satan.

Shell

Shell is the organically formed hard outer part of a saltwater or freshwater animal. Shells of all types have been ...
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Shield Cut

Shield Cut

The term shield cut, as suggested by Tillander, indicates all historical triangular cuts. The basic blueprint comes from half an ...
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Etruscan Revival Cameo Silhouette Hardstone Earrings.

Silhouette

Etruscan Revival Cameo Silhouette Hardstone Earrings.A silhouette (named after French finance minister Etienne de Silhouette) was originally a portrait "en ...
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A New Single Cut.

Single Cut

Old Single Cut An Old Single Cut; a Square Table Cut with Faceted Corners.The Old Single Cut is a variation ...
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Refraction Diagram.

Single Refraction

Refraction Diagram.When a beam of light enters a crystal in the cubic system or an amorphous substance, it does not ...
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Smalti Used to Create Filati and Tesserae.

Smalti, Filati, and Tesserae

Smalti Smalti is a type of glass paste (not as brittle as ordinary glass) with each individual color poured into ...
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Verdura Smoky Quartz and Tourmaline Cocktail Ring This item has been sold

Smoky Quartz

Smoky Quartz is a brownish-black to greyish color variety of quartz. Cairngorm is the Scottish term for smoky quartz.Smokey Quartz ...
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Specific Gravity

Specific Gravity is the ratio of the weight of a substance to the weight of an equal volume of water ...
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Spectroscope

A gemological instrument that separates a ray of light into its spectral colors by means of prisms or a diffraction ...
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Electromagnetic-Spectrum

Spectrum

Introduction The electromagnetic spectrum is best explained with the use of an image. On the right, you see an overview ...
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Cut Spessartite from Loliondo, Tanzania. Image by Tim Spauwen.

Spessartine/Spessartite

Cut Spessartite from Loliondo, Tanzania.Image by Tim Spauwen Spessartine was first discovered in the Spessart Mountains of Germany from which ...
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Vintage Red Spinel Ring

Spinel

Spinel is a magnesium aluminum oxide, occurring in many colors with excellent durability. Natural spinel is really a group of ...
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a 47.32 ct Kunzite, photo courtesy of Constantine Wild, Idar-Oberstein

Spodumene

The name spodumene derives from the Greek meaning burnt to ashes describing the non-gem colorless or gray variety of spodumene. There are ...
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Stability

Gemstone stability refers to the stone's general resistance to fading, heat tolerance and ability to withstand chemical attack ...
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Strass

Glass with high lead content. The lead increases the refractive index, specific gravity and dispersion but lowers the hardness. Strass was invented in the 18th century by ...
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Swiss Cut

Swiss Cut

Swiss cut diamonds are the late 19th-century predecessor to the 20th century Single Cut. Their crowns are built up out of a table facet, ...
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Boule

Synthetic Corundum

External Link History of Synthetic Corundum:  http://www.dtic.mil/dtic/tr/fulltext/u2/a460239.pdf Gems & Gemology: The Quarterly Journal of the Gemological Institute of America. Synthetic Corundum: ...
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Synthetic Diamonds In the Lab.

Synthetic Diamond

Video Presentation on Diamond Synthesis Gems & Gemology: The Quarterly Journal of the Gemological Institute of America. Synthetic Diamond: March-April 1935, ...
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Synthetic Emerald and Diamond Flower Motif Ring

Synthetic Emerald

Synthetic Emerald Created by the Renowned Chatham Company, est.1938, San Francisco. Gems & Gemology: The Quarterly Journal of the Gemological Institute ...
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Art Deco Synthetic Cabochon Sapphire Ring

Synthetic Gemstone

Synthetic gemstones are artificially created gemstones that have the same chemical build up as their natural counterparts. They therefore harbour the same ...
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Table-Cut

Table Cut

The term 'table cut' is used to indicate all types of cuts that have a table facet. Cuts that fall ...
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The Crown is Comprised of the Table, Main, Star and Girdle Facets.

Table Facet

The Crown is Comprised of the Table, Main, Star and Girdle Facets.The table is the largest facet on the crown of a gemstone. This horizontal ...
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5 Egyptian Blue Glaze Amuletic Figures, c.664-525 BC. Photo Courtesy of Sotheby's.

Talisman

The Eye of Horus.Louvre.A talisman is a charm, amulet or other ornament that has a magical meaning to the wearer ...
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Tiffany - Schlumberger Tanzanite and Diamond Brooch.

Tanzanite

Tanzanite is a variety of blue zoisite that was discovered in the Merelani District of Tanzania in 1967. It's compelling ...
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Tassie Ring.

Tassie

Oval Tassie Intaglio Depicting Bearded Priam, King of Troy, in Phrygian Cap. c. Late 18th Century.© The Trustees of the ...
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68.09 ct. Taylor-Burton Diamond, Suspended from an Oscar Heyman & Bros. Necklace. Currently Owned by Mouawad.

Taylor-Burton Diamond

68.09 ct. Taylor-Burton Diamond, Suspended from an Oscar Heyman & Bros. Necklace. Currently Owned by Mouawad. This diamond is a stone whose ...
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Tenebrescence

Tenebrescence is an optical phenomenon, seen in the mineral hackmanite and some others, which resembles phosphorescence. The main difference between phosphorescence and ...
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Thulite (Green) with Ruby (Red)

Thulite

Sources Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 262-264. Schumann, Walter. Gemstones of the World, New ...
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Cartier Tiger's Eye and Diamond Ring

Tiger’s-Eye

Tiger's-eye is chatoyant quartz. It ranges in color from brownish yellow to brown or reddish brown with iron oxide being the ...
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Blue Topaz and Diamond Ring.

Topaz

Topaz is an aluminum, hydroxyl-fluorine silicate, found primarily in gem pegmatites. Minas Gerais in Brazil is the largest producer of ...
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Victorian_Tortoiseshell_Butterfly_Brooch

Tortoise Shell

Tortoise Shell Locket and Chain. Tortoise shell is the name for the outer blades covering the upper shell of the ...
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Art Deco Jade and Diamond Platinum Ring.

Toughness

With regard to gemstone properties, toughness is a resistance to breaking. Many things can have an effect on this property including internal ...
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Art Nouveau Pink Tourmaline Pendant Brooch.

Tourmaline

Tourmaline is a group of minerals displaying the widest variety of gemstone color in the mineral kingdom. The spectral assortment ...
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Carved Nephrite and Amethyst Floral Brooch .

Translucent

To be translucent is to transmit light, but diffusely, so that objects beneath cannot be clearly resolved. Translucent enamel is used to ...
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Transparent Rock Crystal Quartz Bead Necklace.

Transparent

Material through which an object can be viewed clearly, even through a considerable thickness. Transparent Rock Crystal Quartz Bead Necklace ...
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Trapiche Emerald from Muzo Mine, Colombia.

Trapiche

A trapiche emerald is one with a central green area radiating six green arms giving the gem a flower-like appearance. These intense green ...
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Triplet

Triplet

A triplet is a kind of composite stone that contains out of three parts. A good example is the opal triplet which often is ...
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Bohemian Pyrope Garnet Cluster Brooch, c. Mid-19th Century.

Turnau

Turnau is the German name for the town Turnov in the Czech Republic (Bohemia). It has traditionally been the trade ...
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Antique Turquoise and Diamond Ring

Turquoise

Turquoise is chemically a hydrous copper aluminum silicate, occurring in microcrystalline nodules. It has been coveted and admired throughout our ...
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Twinning

Growth process in which a twin crystal is produced. Often seen as fine parallel lines ...
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Tumble Polished Unakite Pebbles.

Unakite

Tumble Polished Unakite Pebbles ...
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Red Vauxhall Glass Maltese Cross Brooch and Earring Suite, c.1825

Vauxhall Glass

Through the eighteenth century and on into the middle of the nineteenth, Vauxhall glass was a popular gem substitute. Intense ...
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Verneuil Ruby showing typical curved striae under magnification

Verneuil

Auguste Victor Louis Verneuil (1856-1913) Auguste Victor Louis Verneuil is the father of gemstone synthesis. Born a watchmaker's son, Verneuil became a ...
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Quartz Crystal with Vitreous Luster.

Vitreous Luster

Vitreous is defined as a glass-like luster. Example: Moonstone can exhibit a vitreous luster. A subvitreous luster is somewhat less glass-like. Edwardian ...
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Wavelength Illustration.

Wavelength

An essential part of understanding color is knowing what light is. Light is electromagnetic energy which is radiated as waves ...
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Natural Burmese Jade Platinum Diamond Ring.

Waxy Luster

Waxy luster describes the luster observed on Jadeite and Nephrite. Art Deco Jade and Diamond Platinum Ring. Carved Nephrite and Amethyst Floral Brooch ...
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Wittelsbach-Graff Diamond.

Wittelsbach

The Wittelsbach-Graff Diamond.Image Courtesy of Christie's Images, 2008 It’s that rare diamond that could match its color to the blue-blood of its ...
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Yttrium Aluminum Garnet - YAG

YAG

Yttrium Aluminum Garnet - YAG ...
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Vintage Blue Zircon RIng.

Zircon

Zircon is a zirconium silicate that crystallizes in the tetragonal crystal system. It is highly dispersive and brilliant. Natural zircons ...
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Thulite (Green) with Ruby (Red)

Zoisite

Zoisite is named for the famed collector Sigmund Zois. Discovered in Austria in 1805 in the Sau-Alp mountains, zoisite was ...
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Notes:

  1. Kunz, pp. 307-337
  2. Esther 1:6