Agate to Zircon
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 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 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 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 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, 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
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 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 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 var. Chiastolite. Gems & Gemology: The Quarterly Journal of...
Andradite
Andradite Garnet var. Demantoid.
Apatite
Gems & Gemology: The Quarterly Journal of the Gemological Institute of...
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 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 is a phenomenon in gemstones whereby glittering reflections of small inclusions of hematite or goethite in feldspar or...
Aventurine
Azurite
Gems & Gemology: The Quarterly Journal of the Gemological...
Azurmalachite
Sources Gem Reference Guide, Los Angeles:...
Benitoite
Gems & Gemology: The Quarterly Journal of the Gemological Institute of...
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 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 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 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 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
A large almandine garnet that is cut en cabochon. These deep purplish-red garnets were popular in Victorian jewelry.
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 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 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. Sources Gem Reference Guide, Los Angeles: Gemological...
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 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 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
French Japonesque Cinnabar, Diamond and Onyx Jabot Pin. Online Texts on CinnabarSome Cinnabar Deposits in Western Nevada by Knopf
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 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 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 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
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
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...
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
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
Grossular Diopside. Photo Courtesy of Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [table id=116 responsive=collapse...
Druse
A surface covered with small projecting crystals, usually lining the sides of a cavity.
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 Crystals. Photo Courtesy of Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [table id=15 responsive=collapse...
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 is an iridescent brown form of chalcedony.
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.
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
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
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
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
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 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 is the strongly pleochroic, bright green variety of spodumene. First discovered in North Caroline by W. E. Hidden in 1879. ...
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
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 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
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 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
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
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 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 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 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
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 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 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...
Kyanite
Labradorite
Labradorite is a mineral species of the plagioclase series of the feldspar group.
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 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
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 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
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...
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 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
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 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
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 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 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...
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 is a mineral species of the plagioclase series of the feldspar group.
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 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 is a mineral series in the feldspar group. Moonstone Sources...
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
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 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 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
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
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 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"...
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
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
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 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 is the name given to rock crystal which is faceted to imitate diamond. It is also a name for colorless paste.
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 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
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 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 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 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 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 is a brown and white banded variety of onyx primarily used in glyptography. Antique Victorian Sardonyx Seal Fob. [table id=183...
Saussurite
Saussurite is a rock formed from green zoisite in combination with epidote, white feldspar and other minerals [table id=185...
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 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
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 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 is a brownish black to greyish color variety of quartz. Cairngorm is the Scottish term for smoky quartz [table id=193...
Spessartine/Spessartite
Cut Spessartite from Loliondo, Tanzania.Image by Tim Spauwen Spessartine...
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
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
External LinkHistory of Synthetic Corundum: http://www.dtic.mil/dtic/tr/fulltext/u2/a460239.pdfGems & Gemology: The Quarterly...
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
SourcesGem Reference Guide, Los Angeles: Gemological Institute of...
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 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 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 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
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 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...
Unakite
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
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...
YAG
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...
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...