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Agate to Zircon

Adularia

Adularia

Adularia is a variety of orthoclase feldspar that is colorless to milky in appearance. It is mineralogically a potassium, aluminum, silicate feldspar found in the Alps which can display a bluish...

Agate

Agate

Agate is a variety of chalcedony found in many different colors and degrees of translucency. There are several varieties of agate named after their location of origin or physical characteristics....

Alabaster

Alabaster

Alabaster is a name used for gypsum and calcite but has also been used to indicate selenite. These minerals are easily worked due to their low hardness and have been used to craft all sort of things...

Alexandrite

Alexandrite

Alexandrite is a variety of chrysoberyl with a distinct change of color when viewed in incandescent and fluorescent light. The colors that Alexandrite occurs in depends on its geographical source...

Almandine

Almandine

Almandine Garnet Ring. 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 information read our...

Amazonite

Amazonite

Amazonite, a variety of the microcline series of the feldspar group, gets its name from the Amazon River. A gridlike structure visable in amazonite gives the stone a faint sheen and...

Amber

Amber

In the forest primeval, a creature calls…Its echo is heard for millions of years.Frozen in time; the drama unfolds--A death struggle painted in amber tears. Amber is the...

Amethyst

Amethyst

Amethyst is the the most coveted member of the quartz family. It can be found in shades ranging from a very deep royal purple with hints of red, to a pale pastel lilac with subtle undertones of...

Ametrine

Ametrine

Ametrine is a variety of quartz consisting of both amethyst and citrine with zones of both purple and yellow. Most naturally occurring ametrine comes from Bolivia, with...

Andalusite

Andalusite

Andalusite var. Chiastolite. Gems & Gemology: The Quarterly Journal of...

Apatite

Apatite

Gems & Gemology: The Quarterly Journal of the Gemological Institute of...

Aquamarine

Aquamarine

Aquamarine is the blue variety of the mineral beryl. Most natural aquamarine is a pale bluish green, which was the preferred color before 1900. Today it is routinely heat treated to remove the green...

Aragonite

Aragonite

Aragonite is a naturally occurring crystal form of calcium carbonate and is a precipitate from salt and freshwater conditions. One form of aragonite occurs naturally in most mollusks. Crystallizing...

Aventurescence

Aventurescence

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

Azurite

Azurite

Gems & Gemology: The Quarterly Journal of the Gemological...

Benitoite

Benitoite

Gems & Gemology: The Quarterly Journal of the Gemological Institute of...

Beryl

Beryl

Beryl is a beryllium aluminum silicate that occurs in every color of the rainbow but is colorless in pure form; various metallic impurities give beryl its varied coloration. When green, it's an...

Biwa Pearl

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 produced by introducing 10 to 20 bits...

Bloodstone

Bloodstone

Bloodstone Intaglio Signet Ring with a Coat of Arms Seal. Tiffany & Co.  Who on this world of ours his eyesIn Aries opens shall we be wiseIf always on his hand there liesA Bloodstone.Kunz...

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 Scotland. During the Victorian period cairngorms were...

Calcareous Concretion

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 of these "pearls"...

Calcite

Sources Gem Reference Guide, Los Angeles: Gemological Institute of...

Calcium Carbonate

Calcium carbonate is a primary component of the shells of marine mollusks and pearls. The outer shells of mollusks are composed of calcium crystals bound by conchiolin. The middle layer...

Carbuncle

Carbuncle

A large almandine garnet that is cut en cabochon. These deep purplish-red garnets were popular in Victorian jewelry.

Carnelian

Carnelian

Carnelian Intaglio Ring. 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...

Cave Pearls

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, they have a porous texture. Cave...

Chalcedony

Chalcedony

Chalcedony is cryptocrystalline quartz. It is semitransparent to opaque and, depending on its color, chalcedony is further divided into several varieties. History All varieties of chalcedony were...

Chlorastrolite

Chlorastrolite

Chlorastrolite. Sources Gem Reference Guide, Los Angeles: Gemological...

Chrysoberyl

Chrysoberyl

Chrysoberyl is among the most brilliant of gems and its hardness is only surpassed by diamonds and corundum. The name chrysoberyl derives from the Greek, meaning "Golden Beryl", although in reality,...

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 Chrysocolla.

Chrysoprase

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 presence of nickel impurities in its crystal...

Cinnabar

Cinnabar

French Japonesque Cinnabar, Diamond and Onyx Jabot Pin.  Online Texts on CinnabarSome Cinnabar Deposits in Western Nevada by Knopf

Citrine

Citrine

Citrine is a yellow or golden variety of quartz, colored with iron. Natural citrine is relatively rare, occurring in Brazil, Madagascar and Myanmar. Most citrine on the market today is actually...

Conch Pearls

Conch Pearls

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 the saltwater giant conch or queen conch shell. Classified as...

Copal

Copal

Copal is a fossilized organic resin. This amorphous yellow to brownish material is often confused with amber, but amber is much older than copal. A test using acetone can separate amber and copal -...

Coque de Perle

Coque de perle, from the French for 'pearl shell' was a Georgian faux pearl carved from the East Indian nautilus shell. The central whorl of the convex part of the shell was cut away to form these...

Coral

Coral

Coral is one of a very few organic gemstones. It consists of a mass of skeletons of tiny marine invertebrates that once lived in a colony attached to rocks or other objects on the ocean floor. The...

Corundum

Corundum

Definition The mineralogical name for Al2O3, the corundum family encompasses the gem varieties sapphire and ruby. It crystallizes in the trigonal structure and is surpassed only by diamond in...

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 Zirconia has a thermal insulating property...

Andradite

Demantoid

Antique Demantoid and Diamond Earrings. At the end of the reign of Nicholas I, Emperor of Russia, and the beginning of the reign of Tsar Alexander II - after whom the...

Diamond

Diamond

Diamonds are valued for their incredible brilliance and hardness. Diamonds are chemically pure carbon, identical to the graphite used for pencils. Diamonds' hardness is the result of extremely...

Diopside

Diopside

Grossular Diopside. Photo Courtesy of Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [table id=116 responsive=collapse...

Druse

Druse

A surface covered with small projecting crystals, usually lining the sides of a cavity.

Emerald

Emerald

Emerald is the green variety of the mineral beryl, owing its vibrant color to a trace amount of chromium and occasionally a slight trace of vanadium. The majority of emeralds contain several...

Epidote

Epidote

Epidote Crystals. Photo Courtesy of Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [table id=15 responsive=collapse...

Feldspar

Feldspar

Feldspar var. Moonstone. Feldspar is a gem group that includes microcline, orthoclase, and plagioclase varieties. Each variety varies as to crystal structure, refractive index, color and...

Fire Agate

Fire Agate

Fire Agate is an iridescent brown form of chalcedony.

Fool’s Gold

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 Pyrite.

Almandine

Garnet

The term garnet applies to a group of minerals with six main varieties. The varieties differ in chemical composition and color but share the same crystal system. These varieties are: Almandine...

GGG

GGG

Gadolinium Gallium Garnet. A synthetic gemstone used as an early diamond substitute. GGG is manufactured by the Czochralski method and can be manufactured in many colors. With its specific gravity...

Glass

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 types of naturally occurring glass: Obsidian, Moldavite and Lybian...

Grossular

Grossular

Tsavorite 1967 - Discovered in Northern Tanzania close to the Kenyan border by Campbell R. Bridges. Mining the deposit wasn't possible in Tanzania so Bridges crossed the border and found the green...

Gueda

The Sri Lankan gueda sapphire is a pale, translucent and, until the discovery of heat treatments, useless variety of sapphire. Once heat treatment techniques were...

Hardstone

Hardstone

Finely Carved Hardstone (Sardonyx) Cameo Brooch. Hardstone is a term used loosely to refer to any hard gem material used for carving. Hardstone is usually presented as cameos and intaglios but is...

Hematite

Hematite

Hematite derives its name from the Greek word haema for blood. Thinly sliced hematite is a reddish color and, when rubbed against a scratch plate, hematite leaves a red streak. While popular in...

Hiddenite

Hiddenite

Hiddenite is the strongly pleochroic, bright green variety of spodumene. First discovered in North Caroline by W. E. Hidden in 1879. ...

Horn

Horn

Horn, commonly used in buckles, brooches, combs and hair ornaments was usually ox-horn, although it could be from any animal. With colors ranging from nearly colorless to deep rich browns, low...

Hornbill Ivory

Hornbill Ivory

In the fall of 2009 Stone Group Labs received an unusual item for identification. It turned out to be manufactured from hornbill ivory. Reported by Cara Williams: Carved Hornbill Clasp. Photo...

Hornblende

Hornblende

Hornblende is a series of minerals, not a mineral in its own right. By composition, it is an iron-magnesium silicate that varies by inclusion of aluminum and calcium. Trace amounts of titanium,...

Hydrogrossular

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 as a jade simulant. Watermelon...

Idocrase

Idocrase

Idocrase is mineral species known as Vesuvianite and has several varieties. Sometimes erroneously referred to as "California Jade." Californite - Mottled or Veined Green to Yellowish Brown Xanthite...

Imitation

An imitation is an object or gemstone which is used to mimic a more valuable object or gemstone. Many synthetic and natural minerals are used to mimic - for example - diamond. Another word for...

Iolite

Iolite

Etymology The name, iolite, originates from the Greek word “iodes” meaning violet. It is often found under the misleading name of water sapphire. Iolite Facts The gemstone iolite is the transparent...

Ivory

Ivory

Historically, this organic gem material referred to as Ivory came only from elephant tusks. Since elephants have become a protected species and the sale of elephant ivory has been outlawed, most of...

Jade

Jade

Jade is in the gemstone family that includes both Jadeite and Nephrite. The term Jade is still often interchanged with jadeite and nephrite without regard to the fact that they are different...

Jadeite

Jadeite

Jadeite is a silicate containing sodium and aluminum. Jadeite occurs in a very wide range of colors, translucencies and textures. In jewelry, jadeite is the more valuable of the two varieties of...

Jasper

Jasper

Jasper Cuff Links. Jasper is a member of the chalcedony family of gemstones. The name is of Greek derivation meaning spotted stone. Throughout history, it has been used for...

Jet

Jet

A Jet Box with a Pietra Dura Inlay. et is a type of brown coal used since the Stone Age for personal adornment. Formed from the fossilized wood of a Jurassic period tree that...

Kashmir Sapphire

Kashmir Sapphire

Kashmir Sapphire and Diamond Ring. Undoubtedly, the rarest and most beautiful of all sapphires are the legendary Kashmir. As befitting such otherworldly gems, Kashmir Sapphires originate in a...

Kunzite

Kunzite

Kunzite and Diamond Ring. Kunzite, a variety of spodumene, was named for George F. Kunz who was the first to describe this gem in 1902. Gem kunzite is a rose-violet color with strong pleochroism. It...

Labradorite

Labradorite

Labradorite is a mineral species of the plagioclase series of the feldspar group.

Lapis Lazuli

Lapis Lazuli

Lapis lazuli is a rock aggregate made up from - predominantly - the minerals lazurite, sodalite, nosalite and hauyne. It has a typical cobalt blue color, often with patches of pyrite (golden) and/...

Malachite

Malachite

Malachite is green stone with irregular bands of lighter and darker green. The name malachite comes from the Greek word malache which means mallow, for the mallow leaf of the same hue. Malachite was...

Mallorca Pearls

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 founded by Eduardo Hugo Heusch in 1890. Created with a core of...

Marcasite

Marcasite

Marcasite is an iron sulfide mineral with an orthorhombic crystal structure. It is very brittle and unsuitable for jewelry. What we call "marcasite" in jewelry is actually pyrite - "fools gold" -...

Mexican Fire Opal

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 well as faceted. The source for this gem material is...

Amazonite

Microcline

Amazonite in Albite Specimen. Photo: Rob Lavinsky, iRocks.com Microcline is a mineral series in the feldspar group. Amazonite is a light green to greenish blue variety of Microcline. Sometimes...

Moldavite

Moldavite

Moldavite is formed from melted rock resulting from a meteorite strike. The surface of these small specimens can be rippled (roiled), wavy, pitted and generally not smooth. Not usually seen in...

Montana Sapphire

Montana Sapphire

Tiffany Iris Corsage Brooch Set With Montanna Sapphires. © The Walters Art Museum. While most are familiar with the exotic beauty and rarity of Kashmir and Ceylon sapphires, the state of Montana is...

Moonstone

Moonstone

Moonstone is a variety of orthoclase feldspar, which is a sodium aluminum silicate. Moonstones can occur colorless, blue-white, white and pale shades of apricot and peach. The rarest and most...

Moss Agate

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 of the moss agate can be...

Mother-of-Pearl

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 and other decorative purposes. It is composed of calcium carbonate bound...

Nephrite

Nephrite

Nephrite Nephrite is a magnesium and calcium silicate with an interlocking fibrous structure that gives it extreme toughness. It is a member of the Tremolite/Actinolite Series in the Amphibole...

Glass

Obsidian

Obsidian. Obsidian is a naturally occurring glass of volcanic origin, having an amorphous structure due to rapid cooling. It can be gray to black and often displays splotchy white patches or...

Oligoclase

Oligoclase

Oligoclase is a mineral species of the plagioclase series of the feldspar group.

Onyx

Onyx

Onyx is a variety of cryptocrystalline silicon dioxide or chalcedony. It is banded with contrasting colors making it an excellent medium for three dimensional cameo and intaglio style carving....

Opal

Opal

Opal is a hydrous variety of silicon dioxide. It is unlike other minerals because it is not crystalline! Opal is made up of sub-microscopic silica spheres, bonded together with silica and water. The...

Opaline Glass

Opaline glass was a gem imitation with a milky white to blue appearance generally cut en cabochon a popular daytime "gem" in the Georgian era. Foilbacked with metallic colored foils helped give the...

Orthoclase

Orthoclase

Orthoclase is a mineral series in the feldspar group. Moonstone Sources...

Paraíba

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 colors. It was discovered in 1989 in the Paraiba...

Pearl

Pearl

Pearls are organic gems, produced in pearl oysters. Pearl oysters are not edible, and edible oysters do not produce gem quality pearls. When an irritating foreign particle becomes lodged within the...

Peridot

Peridot

Peridot is the gem variety of the mineral chrysolite or olivine. It is a silicate of iron and magnesium found in basaltic igneous rocks. Although the mineral is fairly common, gem quality specimens...

Petrified Wood

Petrified Wood

Petrified Wood is is wood that has been replaced by chalcedony aka silicified wood. In looks, it is very similar to patterned agate. Petrified Tree in Petrified Forest National Park, USA. Image by...

Plastic

Plastic

Plastics are man-made substances used in jewelry to imitate natural gem materials. Early plastics were organically derived, like the combination of casein and lye. With Charles Goodyear's...

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. Dyed...

Prasiolite

Prasiolite

Prasiolite is the green variety of Quartz. The material is extremely rare in nature and is only found in a handful of deposits. The gem gets its name from the Greek prason meaning "leek"...

Fool’s Gold

Pyrite

Pyrite is an opaque yellow mineral with a metallic luster. Its cubic crystal system is evident in its outward appearance and specimens are often cube-shaped. Pyrite. [table id=176...

Pyrope

Pyrope

Bohemian Garnet Earrings. The Czech Republic; for over 600 years the so-called 'Bohemian Garnets' have formed the bulk of pyropes used in jewellery. Especially in Victorian times, these garnets were...

Quahog

Quahog

A quahog is a bivalve clam native to the eastern seaboard of the United States. Used mostly as a food source, these clams occasionally produce a pearl-like gem in a beautiful natural purple color....

Quartz

Quartz

Quartz is a commonly occurring variety of silicon dioxide. It often crystallizes into well-formed hexagonal prisms. Quartz occurs in many colors, purple amethyst, pink rose quartz, yellow citrine,...

Rhinestone

Rhinestone

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

Rhodochrosite

Rhodochrosite

Rhodochrosite is a manganese carbonate mineral with a transparent to translucent rose-pink color with undulating bands of white, gray or brown. The name derives from the Greek rhodon, meaning rose,...

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 for beads. The name is derived from the...

Rock Crystal

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 name Rock Crystal. This transparent colorless form...

Rose Quartz

Rose Quartz

Rose quartz gets its name from its rosy pink color. Because of its massive turbid crackled nature rose quartz is often carved or typically cut en cabochon or as beads. Only very large, clear pieces...

Ruby

Ruby

Ruby is the red variety of sapphire or the mineral corundum. When corundum occurs in any color, other then red, it is referred to as a sapphire. Rubies are primarily mined in Burma, Madagascar,...

Sapphire

Sapphire

Sapphire is a variety of the mineral corundum that occurs in spectacular colors with great durability and stability. When corundum is red, it is termed a ruby. All other colors, including pink, are...

Sard

Sard

Sard is a translucent to semi-transparent variety of chalcedony. The colors are similar to carnelian but they are darker and less saturated in red-brown to brown or dark orange. Carved Sard Indian...

Sardonyx

Sardonyx

Sardonyx is a brown and white banded variety of onyx primarily used in glyptography. Antique Victorian Sardonyx Seal Fob. [table id=183...

Saussurite

Saussurite

Saussurite is a rock formed from green zoisite in combination with epidote, white feldspar and other minerals [table id=185...

Seed Pearl

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 naturally and were used as a decorative border, as...

Serpentine

Serpentine

Serpentine is not a single crystal gem, but a rock-forming mineral group. The name may derive from the Latin serpentinus due to its scaly appearance and green color. Serpentine is often carved as...

Shale

Shale

A fissile (easy to split) sedimentary silicate-rich rock with particles mostly in the silt and clay size. The color is usually a tone of gray but can be brown, red or green to black. Shale was used...

Shell

Shell

Shell is the organically formed hard outer part of a saltwater or freshwater animal. Shells of all types have been used in jewelry since we first began to adorn ourselves, early beads and pendants...

Smoky Quartz

Smoky Quartz

Smoky Quartz is a brownish black to greyish color variety of quartz. Cairngorm is the Scottish term for smoky quartz [table id=193...

Spinel

Spinel

Spinel is a magnesium aluminum oxide, occurring in many colors with excellent durability. Natural spinel is really a group of related minerals in which its magnesium is substituted with other...

Spodumene

Spodumene

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

Synthetic Corundum

Synthetic Corundum

External LinkHistory of Synthetic Corundum: http://www.dtic.mil/dtic/tr/fulltext/u2/a460239.pdfGems & Gemology: The Quarterly...

Tanzanite

Tanzanite

Tanzanite is a variety of blue zoisite that was discovered in the Merelani District of Tanzania in 1967. It's compelling beauty immediately won over the hearts of everyone that laid eyes on it, and...

Thulite

Thulite

SourcesGem Reference Guide, Los Angeles: Gemological Institute of...

Tiger’s-Eye

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 coloring agent. The gemstones fibrous structure causes it to be...

Topaz

Topaz

Topaz is an aluminum, hydroxyl-fluorine silicate, found primarily in gem pegmatites. Minas Gerais in Brazil is the largest producer of topaz. A common, yet mistaken belief is that all topaz is...

Tortoise Shell

Tortoise Shell

Tortoise Shell Locket and Chain. Tortoise shell is the name for the outer blades covering the upper shell of the Hawksbill turtle and the Loggerhead turtle. Tortoise shell has been valued for use in...

Tourmaline

Tourmaline

Tourmaline is a group of minerals displaying the widest variety of gemstone color in the mineral kingdom. The spectral assortment of color in tourmaline is a result of substitutions of transition...

Trapiche

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 areas are outlined by dark or black albite or...

Turquoise

Turquoise

Turquoise is chemically a hydrous copper aluminum silicate, occurring in microcrystalline nodules. It has been coveted and admired throughout our history because of its magnificent color. Turquoise...

Vauxhall Glass

Through the eighteenth century and on into the middle of the nineteenth, Vauxhall glass was a popular gem substitute. Intense hues of highly reflective purple, orange, red, green and blue were set...

Verneuil

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 chemist's laboratory assistant at age...

Zircon

Zircon

Zircon is a zirconium silicate that crystallizes in the tetragonal crystal system. It is highly dispersive and brilliant. Natural zircons range from colorless to pale yellow or green. These colors...

Thulite

Zoisite

Zoisite is named for the famed collector Sigmund Zois. Discovered in Austria in 1805 in the Sau-Alp mountains, zoisite was not always considered gem material. A green specimen with hornblende...