Abalone is a mollusk whose shell is iridescent on the inside which and used as a source of mother of pearl.

Acroite is a rare, colorless variety of tourmaline.

Adularia is a common type of moonstone and is usually set as a cabochon. It was very popular early in the 20th century and extensively used in Art Nouveau jewelry.

African Emerald is a misnomer for green fluorspar that is mined in South Africa and it is not an emerald at all.

African Jade is not jade but a misnomer for massive green grossular garnet that is mined in South Africa It does look like jade and can be light green, white, or pink. It is also called Buddstone, Garnet Jade, Grossular Garnet, South African Jade and Transvaal Jade.

Agate is a stone with distinct and dramatically banded stone composed of quartz layers. This composition varies greatly and can be of many colors. Agates tend to be translucent or at least contain translucent bands being composed of microscopic "fibers" of crystalline quartz. Each individual agate forms by filling a cavity in a host rock. As a result, agate often is found as a round nodule with concentric bands like the rings of a tree trunk. There are many specific colorations of agates that have been given variety names.

Alexandrite is a gem type of chrysoberyl that appears to be different colors depending on whether it is viewed in natural or artificial light. Alexandrite appears to be red when seen in candle light and blue to green when seen in fluorescent light. Alexandrite was discovered on the birthday of the Russian Czar Alexander II, and it was named in his honor. Alexandrite is mined in Russia, Brazil, Burma, Ceylon, and Rhodesia. Laboratory-produced alexandrite is common, and it is often sold as natural alexandrite.

Almandine is the most common type in the Garnet family. It is violet-tinged and ranges in color from deep red to reddish-brown. Some Almandine garnets display asterism when polished as cabochons and are known as "Star Garnets”.

Amazonite is an iridescent variety of microcline used as a semiprecious stone. It ranges in color from green to blue-green. Most Amazonite is opaque often found with white, yellow or gray inclusions and a silky luster or silvery sheen but rare crystals are transparent.  It is usually set as a cabochon since it breaks easily if faceted. Amazonite should be cleaned in lukewarm soapy water, never with a steamer or ultrasonic cleaner.

Amber is the fossilized tree resin of now-extinct conifer trees and ancient pines that hardened and became preserved in the earth's crust for millions of years. It one of the few organic gemstones and comes in many colors including yellow, reddish, whitish, black, and blue. It is flammable and can usually be distinguished from plastics and glasses by its inclusions and its ability to float in salt water.

American Ruby is actually a semi-precious pyrope garnet and not a ruby. It is has a deep red color.

Amethyst is a form of the mineral quartz and relatively common gemstone. It is usually purple, but ranges in color from pale lavender to a very deep, reddish purple to a milky color to green. Deeper-colored amethysts are more highly valued. Most Amethyst is faceted into jewelry cuts, and some are cut as cabochons.

Ametrine is a variety of quartz, a mixture of amethyst and citrine. It is partially purple and partially orange-yellow with the color zones often sharply divided. It is found only in the Anahi mine in Bolivia.

Ammolite is a fossilized, opal-like ammonite shell used as a gemstone. It is a gray, iridescent stone with flashes of green, red, yellow, blue or purple (blues and purples are rare); the color changes as the stone is turned. It is also known as korite, calcentine, or Buffalo Stone. Ammolite is usually treated with a colorless, hard material to increase the strength of the stone and is often mounted as a doublet or a triplet. It is only found in southern Alberta, Canada.

Andalusite is highly pleochroic gemstone, that is the angle of light refraction makes the wide array of colors seen in the stone. Typical colors include green, brown, red and yellow. The angle at which the stone is cut directly affects the resulting color of the stone.

Apache Tears is a type of obsidian (volcanic glass) that is usually black, but is occasionally red, brown, gray, green (rare), dark with "snowflakes," or even clear.

Apatite is a clear to opaque stone that comes in many colors, including green, yellow, blue, violet, and yellow-green called asparagus stone. Some apatite stones show a cat's eye asterism. This stone is rarely used in jewelry because it is brittle and soft.

Aquamarine belongs to the beryl gemstone family. Gem-quality aquamarine is usually free of inclusions and possesses a superior brilliance, while bead-grade aquamarine tends to have many interesting inclusions and numerous opaque areas. The more intense the color of this stone, the higher its value. It ranges in color from light blue to sea-green. Today, blue aquamarines are more highly valued, but this was not true in the past, when sea-green stones were prized.

Arizona Ruby is actually a semi-precious pyrope garnet and not a ruby. It is has a deep red color.

Arizona Spinel is actually a garnet and not a ruby.

Arkansas Diamond is actually a rock crystal, the purest form of quartz and considered a semi-precious stone. It is transparent and often faceted in the likeness of diamonds.

Aventurine also called goldstone and its often used misspelling Adventurine, is a translucent to opaque, massive variety of Quartz containing small inclusions of one of several shiny minerals which give the stone a glistening, ore aventurescence effect. The color depends on the mineral included in the stone. Mica inclusions give a yellowish or silverish glitter or sheen. Goethite and Hematite inclusions give a reddish or grayish glitter or sheen. Fuschite inclusions give a greenish sheen. Aventurine may be green, orange, brown, yellow, or gray. All colors may be used in jewelry, but the green type is by far the most desirable. Aventurine is cut and polished into cabochons and beads for jewelry.

Aventurine Feldspar is also called Sunstone. This gemstone varies from golden to orange to red-brown, and can be transparent or translucent. Sunstone is metallic-looking due to sparkling red, orange or green crystalline inclusions of hematite or goethite crystals.

Aventurine Quartz is a type of quartz with sparkling inclusions of mica or iron. Colors include red-brown, yellow, gray, and green. This stone is usually cut with a flat or rounded surface to maximize its sparkle.

Azurite is a copper-based blue mineral often used in jewelry. Color ranges from very deep blue to pale blue. It usually occurs with green Malachite, which may form green stains or specks on Azurite crystals or aggregates. The two minerals sometimes occur admixed or banded together, forming what is called "Azure-malachite". It is sometimes coated with a colorless wax or impregnated with plastic in order to enhance the color and increase the hardness.

~ B ~

Benitoite is a rare, blue gemstone that is found mostly in the San Benito River in San Benito County, near Coalinga, California. It is strongly dichroic; blue when viewed from most directions, colorless when viewed in a single direction. it is the only known ditrigonal-dipyramidal crystal.

Beryl is a family of colorful gemstones that include emerald (green), aquamarine (blue), Bixbite (red), morganite (pink), heliodor (yellow), Riesling (pale green with warm golden yellow flash), and goshenite (colorless).

Black Moonstone is a type of labradorite that is black with bluish inclusions and not true moonstone. It is usually cut with a flat surface in order to highlight the flashes of color.

Black Opals are a variety of precious opals found in Australia with a dark ground color. They are luminous, iridescent, and frequently have inclusions of many colors, i.e. "fire".

Bloodstone is also called heliotrope and an inexpensive type of chalcedony that is green with red highlights (caused by iron oxide). It is a dark-green variety of chalcedony (quartz) dotted with nodules of bright-red jasper. Polished sections therefore show red spots on a dark-green background, resembling drops of blood and inspiring its name.

~ C ~

Cairngorm is the yellow-brown type of smoky quartz that is often used in traditional Celtic jewelry. The supply of cairngorm is virtually exhausted.

Calcite  is a very common mineral that comes in a wide variety of forms, shapes and colors. Calcite is often fluorescent, and a small amount of manganese is enough to make it glow red under UV light. It also exhibits strong double refraction making anything observed through the crystal appear as double.

Carnelian is also called cornelian and carneole. It is an orange-red form of chalcedony (microcrystaline quartz). When it grades into brown it is known as Sard. When it contains bands of white, it is known as Sardonyx. It is generally cut into cabochons or beads. Most commercial carnelian is really stained chalcedony.

Chalcedony is a catch-all term for microcrystalline quartz. As a marketing term in the gemstone industry, "chalcedony" refers more specifically to semi-transparent or translucent chalcedony with a solid color (commonly pale bluish-gray) and nearly wax like luster. The color can also be white, blue, purple, pink, yellow, orange or red. The orange-red, is known as carnelian. Blue and purple are the most popular hues. The stone is extremely porous, so it takes dye easily and is frequently enhanced.

Chrysanthemum Rock is a black and white rock made up of Gypsum clay, Dolomite and Limestone, with internal crystals of Calcite, Feldspar, Celestite or Andalusite in patterns which can resemble Chrysanthemum flowers or Star Bursts or Snowflake crystals. These stones have been found in Japan, Canada, China and the USA.

Chrysoberyl is a family of stones ranging in color from yellow, to brown, to green. Some chrysoberyls include alexandrite and Cat's Eye.

Chrysocolla is an opaque blue to blue-green mineral sometimes used in jewelry, usually cut as a cabochon.

Chrysolite is a synonym of Olivine (i.e. contains half Forsterite and half Fayalite and may also refer to any Olivine that is yellow-green in color. The name is incorrectly used in describing two minerals: Chrysotile and sometimes in the gem trade to describe yellow, transparent Chrysoberyl.

Chrysoprase is one of the most valuable chalcedony (quartz) gemstones, prized for its rarity and opalescent apple-green color. The more translucent the gemstone, the better the quality.

Cinnabar is the mineral mercury sulfide with a color ranging from cinnamon to scarlet to brick red and can be translucent to transparent. It is very soft and often carved.

Citrine is a rare yellow type of quartz that ranges in color from pale yellow to orange to golden brown. The best quality citrine is found in Brazil. Many stones sold as citrine are actually heat-treated amethysts.

Coral is one of the few organic gems. It is an animal that grows in colonies in the ocean and ranges in color from pale pink (angelskin coral) to orange to red to white to black. The most valued colors are deep red (noble coral) and pink. In jewelry making, coral is either carved into beads, cameos and other forms, or is left in its natural branch-like form and just polished. It used to be thought that coral protected the wearer, so it was a traditional gift to children.

Corundum is called ruby or sapphire, depending on the color which depends on which metallic oxides are present: Rubies contain chromic oxide, blue sapphires contain titanium, yellow sapphires contain ferric oxide. In its rare pure colorless form it is called white sapphire.  Other impure forms are opaque. All corundum stones can asterisms.

~ D ~

Demantoid Garnet is the valuable green colored version of garnet with a cubic crystalline structure. It ranges from yellowish-green to brownish green with a golden shine with deep emerald green being the most valuable. They are more dispersive than diamond.

Diamonds are made of highly-compressed carbon and are one of the hardest materials known. Colors range from colorless, yellow, orange, brown, to almost black. Rarer colors are red, blue, green, and purple; these colors (called fancies) are quite valuable. A diamond's value is based on the "4 C's": color, cut, clarity, and carat weight.

Diopside is a common calcium magnesium silicate that crystallizes from magma. It is the deep green chatoyant or double chatoyant forms. and a variety termed violane that is a blue-violet.

Dumortierite is a blue to violet silicate mineral sometimes used as a semi-precious stone in jewelry.

~ E ~

Emeralds are the green color of beryl. Emerald's precious green color is caused by small amounts of chromium and some vanadium impurities, and enhanced by traces of iron. Unlike other beryls, emeralds often contain inclusions and other flaws called jardin. These flaws are not considered negative aspects, instead they are part of the character of the stone and may verify its authenticity to the purchaser.

Eudialyte occurs in distinct colors of a red-violet, pink, blue, yellow, and brown. It is a rare cyclosilicate mineral rarely forming good crystals and its rarely used as a gemstone, more of a collectible curiosity.

~ F ~

Fire Opal is term for an opal that is fiery orange to red in color but without opalescence, generally milky.

Fluorite occurs in many colors including purple, colorless, red, pink, yellow, green, blue, black, yellow, and multi-colored stones. Crystals are transparent to translucent. Fluorite is relatively soft and easily scratched limiting its use in jewelry.

~ G ~

Gagate is more commonly known as jet and is a variety of coal called lignite. It is frequently carved or cabochon cut.

Garnet is any of a group of semi-precious silicate stones occurring in all colors but blue. Some garnets used as gemstones include pyrope (deep red garnet), almandine (orange-red), spessartine (yellow-orange), grossular (colorless, orange, red, pink or brown), an  iron-aluminum dark red calledcarbuncle stone, Uvarovite (rare emerald green), Andradite (yellow-green to orange-yellow to black), Demantoid (green to yellow-green), Topazolite (yellow-orange-yellow), and others.

Gaspeite is a pale green to apple-green semi-precious gemstone, often with brown inclusions of host rock. It is translucent to opaque and only recently been used in jewelry.

Goldstone or aventurine and commonly misspelled adventurine, is a quartz stone that ranges in color from yellow to red to light green to light brown. The shimmer is caused by tiny metallic particles (mica) within the stone.

Goshenite is the pure, colorless form of beryl.

Grape Garnet is a rare, intense violet to purple-red garnet ade up of almandite and spessartite forms or garnet.

Green Garnet is a Demantoid garnet. They are a rare variety of andradite and have characteristic inclusions that look like horsetails.

Greenstone is another name for nephrite, a variety of jade. It is often veined and used in carvings.

Grossular Garnet is a type of garnet with many different colors and associated names. Hessionite is a transparent brown, yellow, orange, or honey-colored variety often used in jewelry. The yellow variety is called cinnamon stone, hyacinth or jacinth. Transvaal is green to gray. Pink varieties include landerite, rosolite, and Xalostocite. Tsavorite is an emerald-green grossular garnet.

~ H ~

Hackmanite is a vibrant pink variety of sodalite that exhibits tenebrescence. It fades to colorless when exposed to light but will revert when placed in the dark or exposed to shortwave ultraviolet light.

Heliodore is the golden yellow or golden green variety of beryl.

Heliotrope is another name for bloodstone.

Hematite is a lustrous, opaque, blue-black to silvery gray mineral that almost looks like metal. It is often used in jewelry as beads, faceted, carved or cut as a cabochon.

Herkimer Diamonds are not a diamond but are considered and treated by some as a gemstone. They are clear, lustrous, doubly terminated crystals of quartz. They also are called These "Middleville Diamonds" or "Little Falls Diamonds."

Hessonite is also called "cinnamon stone" and is the cinnamon-brown to orange gemstone variety of grossular garnet.

Howlite is a soft, white to gray mineral that takes dye very easily, and can be dyed to imitate turquoise and Lapis Lazuli very well.

~ I ~

Indicolite is a green to blue-green variety of tourmaline.

Iolite is also knows as the mineral cordierite and sometimes called water sapphire and lynx sapphire. The name means 'violet stone' and is a transparent, violet-blue, light blue, or yellow-gray and pleochroic; a single stone will show many colors.

Ivory is one of the few organic gemstones. It generally refers to ivory from elephant tusk but can also refer to the bones and teeth of elephant, narwhals, walrus, hippos, and cachalot whales. It is most often carved or made into beads.

~ J ~

Jacinth is a semi-precious stone also known as hyacinth and is a lustrous orange-yellow, orange-red, or yellow-brown type of zircon. Sometimes, topaz and grossular garnet of this color are also referred to as hyacinth erroneously.

Jade is a semi-precious stone that ranges in color from green to white to lilac to brown to almost black. Translucent jade is more highly valued than opaque jade. Jade is often cabochon set; stones with imperfections are often carved. Two different minerals are called jade: jadeite, harder and usually used in jewelry production, and softer and often veined Nephrite is used in carvings.

Jadeite is one of the mineral forms called jade. It occurs in a wide range of colors, textures and translucencies.

Jasper is a common, opaque, semi-precious stone that is found in many colors, including white, brown, yellow, red, and green. It is often striped, speckled, and multi-colored. It is a type of quartz belonging to the chalcedony family.

Jet is also known as gagate and is one of the few organic gemstones being variety of coal called lignite. It is a lightweight lustrous black stone that was used in mourning jewelry during the Victorian era. Most jet is from Whitby, England. It is rather fragile but lends itself well to carving or is made into cabochons.

~ K ~

Kunzite is a transparent pink, light pink, or light purple gemstone and is a variety of the mineral spodumene. Kunzite can fade after prolonged exposure to light so is best worn at night. The original color of some kunzite stones can be restored or even intensified by irradiation. It is a highly dichroic gem: In one direction, it will appear pink, violet or lilac, and in the other direction, it will appear colorless. It is usually used as a large stone and is easily chipped; small stones are difficult to cut.

Kyanite is a deep sapphire blue, green, gray, or white where the color is not always uniform; it can be blotchy or in streaks. The crystals are transparent to translucent and its hardness varies depending on which way it is scratched due to its long, thin crystals.

~ L ~

Labradorite is a grayish mineral that has brilliant flashes of color, usually green, blue or red, after it is polished. The effect being called labradorescence or schiller. The crystals are transparent to translucent. There is a darker variety of labradorite called "black moonstone" which has bluish inclusions. Labradorite is usually cut with a flat surface in order to highlight the flashes of color.

Lapis lazuli is a rich blue opaque, semi-precious stone that has been used in jewelry since ancient times. It is not a mineral, but a rock consisting of as many as 15 different minerals. The primary minerals present in lapis are lazurite, hauyine, diopside, calcite and pyrite. It chips and scratches easily and water can dull it sheen.

Larimar is a form of pectolite with copper found only in a single place in the Dominican Republic. It is an opaque sky blue stone with white streaks and often with some red to brown impurities. It is usually shaped and polished and not faceted.

Lepidolite is an uncommon mica and is a by-product of lithium mining and owes its color to lithium's proximity.

Lodolite is a variety of quartz with inclusions of chlorite, iron and calcite. These minerals decorate the colorless stone with green, pink, yellow, brown, white and red. Their patterns have been compared to moss and an underwater scene.

London Blue Topaz is the darkest blue variety of topaz.

~ M ~

Malachite is an opaque semi-precious stone with various shades of green, often banded. It is about 57% copper. Malachite was used as jewelry thousands of years ago by the ancients Egyptians. Malachite is usually cut as beads or in a cabochon.

Marcasite is the name given to the mineral iron pyrite that is faceted for use in jewelry. Marcasite and pyrite are both iron disulfides but they are different minerals because they crystallize in different systems and form under different geologic conditions. Marcasite isn't suitable for use in jewelry because it is unstable and can decompose in the air, appearing to acquire a chalky coating.

Maw Sit Sit is an aggregate of numerous minerals, the six main components are: Chromite, ureyite, chrome-jadeite, symplektite, chrome amphibole, and a matrix of lighter minerals. This material is opaque to translucent with flowing veins of green and black. The matrix is dark green to black in color.

Michigan Picture Rock is also know as Pink Kona Dolomite and named after the Kona Hills South of Marquette, Marquette County, Michigan come in many shades of red, orange, brown, yellow, pink, cream, and often has shades of turquoise, brown, cream, gray and black banding, lacing and mottling. Often they will have inclusions of a dark Red Crystal Dolomite (Mooseblood Dolomite) and this is the only place in the world where that particular color of Red is found.

Moldavite is the only known gem-quality stone of extraterrestrial origin. A member of the tektite family, it is believed to be the outer surface of meteorites that fused and melted during entry into our atmosphere. Inclusions of gas bubbles and iron/nickel spherules are common. This natural glass has been used for jewelry, religious articles, and decorative objects since prehistoric times.

Moonstone is a variety of albite feldspar and occur colorless, white, blue-white, and pale shades of peach and apricot. The rarest and most expensive will be colorless with a floating blue color that seems to hover above the stone, a phenomenon termed adularescence.

Morganite is the transparent to translucent the pink, peach or lilac variety of the mineral beryl.

Mother of Pearl or Nacre is the iridescent substance that forms the lining of the shells of some fresh-water and some salt-water mollusks. It is composed of alternate layers of the aragonite form of calcium carbonate and conchiolin.

Moukaite is a semi-precious gemstone variety of jasper from Australia. It varies from red-browns to pinks, with gold and white bands.  

~ N ~

Nephrite is one of two minerals considered to be jade, the other being jadeite.  Nephrite is slightly softer that jadeite and is often veined; it is used in carvings and for making beautiful bowls and vases. Nephrite has been prized by the Chinese as a very tough mineral and was originally used in primitive times to fashion tools such as axes, knives and clubs.

~ O ~

Obsidian is a volcanic glass that is usually black, but is occasionally red, brown, gray, green (rare), dark with "snowflakes," or even clear. It is formed when viscous lava cools rapidly that minerals do not have time to crystallize. Most obsidian is 70 percent silica.

Onyx is a semi-precious stone a variety of chalcedony. It is white, black, brown or red alternating bands. It is different from regular agate in that the bands are parallel and regular and as such lends itself to cameo making.

Opal is a hydrous, silicon dioxide and is unlike other minerals because it is not crystalline but amorphous. It is considered to be a hardened jelly. Water content varies from about 6 to 10% in gem opals. Gem opals are those with a play of color and/or transparent orange varieties. Varieties include White (white or light body with play of color), Black (black to dare green body with play of color), Fire (transparent or translucent or or red with no color play, and Water (colorless with play of color).

~ P ~

Padparadscha Sapphire is a rare pink-orange variety of corundum. It is also spelled padparadschah.

Pearls are organic gems grown within oysters and some other mollusks.  They form when a foreign object acts as an irritant and the mollusk secretes nacre, a lustrous substance that coats the foreign body in layers and eventually a pearl is formed. Types of pearls include: Natural Pearls are made with no human interference; Cultured Pearls made by inserting a bit of a mother-of-pearl or foreign tissue; Baroque Pearls are irregularly-shaped pearls; Freshwater Pearls from fresh water mollusks; Seed Pearls are tiny pearls; Biwa Pearls are a type of freshwater pearl from Lake Biwa, Japan; Blister Pearls grow attached to the shell; Black Pearls are gray to black pearls; and Mabe Pearls that are cultivated blister pearls.

Peridot is the yellow-green semi-precious stone that is the transparent, green form of olivine. Peridot exhibits double refraction; when you look through the stone, things appear double.

Pink Kona Dolomite is also know as "Michigan Picture Rock" and named after the Kona Hills South of Marquette, Marquette County, Michigan come in many shades of red, orange, brown, yellow, pink, cream, and often has shades of turquoise, brown, cream, gray and black banding, lacing and mottling. Often they will have inclusions of a dark Red Crystal Dolomite (Mooseblood Dolomite) and this is the only place in the world where that particular color of Red is found.

Pyrite is faceted into small reflective stones and used in jewelry but erroneously called Marcasite. Marcasite and pyrite are both iron disulfides but they are different minerals because they crystallize in different systems and form under different geologic conditions. Marcasite isn't suitable for use in jewelry because it is unstable and can decompose in the air.

Pyrope Garnet is the deep red color of garnet.

~ Q ~

Quartz is a crystalline mineral that occurs in two varieties: macrocrystalline where crystals recognizable with the naked eye and microcrystalline or cryptocrystalline where crystals too small to see without high magnification. Macrocrystalline forms includes citrine, amethyst, aventurine, hawks-eye, tigereye, rose, rock crystal, flake, rutilated, and smoky. Rutilated quartz and tourmalinated quartz have needle-like inclusions of other minerals. The second, cryptocrystalline, is more commonly known as chalcedony and includes agate, jasper, carnelian, onyx, bloodstone, aventurine, and crysoprase.

~ R ~

Rhodochrosite ranges from rose to pink to almost yellow or brown. It is used in jewelry and for carvings and figurines but is very soft and brittle.

Rhodolite is a purple-red to pink-red variety of garnet.

Rhodonite is a member of the pyroxene group of minerals with a rose-red color.

Rock Crystal is the transparent and purest form of quartz and a semi-precious stone.

Rubellite is a red variety of tourmaline that is red in both incandescent light and daylight making it more valuable than other varieties of red tourmaline.

Ruby is a member of the corundum family and range color from the classic deep red to pink to purple to brown. Rubies are extremely hard; only diamonds are harder. The most valuable will be a dead red in color, without any modifying tones of violet, orange or brown and are transparent in clarity. The most famous source of fine rubies is Myanmar (Burma). A fine ruby brings the highest price of any stone in the world.

Rutilated Quartz is quartz that contains long, fine needles of rutile (titanium dioxide) crystals. It is usually cut as a cabochon.

~ S ~

Sapphire is a member of the corundum family occurring in all colors, with blue being the more commonly associated and the exception being red and then its called ruby. Sapphires are extremely hard; only diamonds are harder and can also exhibit asterism (star sapphire) and color changing depending on whether they are viewed in daylight or incandescent light.

Sard is a semi-precious stone brown to brownish-red, transparent to translucent variety of Chalcedony (Agate). When it grades into brown it is known as Carnelian. When it contains straight, parallel bands of white or black, it is known as Sardonyx.

Sardonyx is a variety of agate where the banding lines are straight and parallel, and consistent in band size. The color of the bands are brown to red, and alternate with white or black bands. It is often carved into ornamental figures, cameos, beads, and cabochons.

Smoky Quartz is a type of brownish quartz that has a smoky look.

Sodalite is a dark blue mineral with streaks of white, gray, pink, or green. It is used for carvings and jewelry as cabochons and beads. It is one of the mineral components of lapis lazuli.

Spectrolite is another name for Labradorite.

Spinel is a hard semi-precious stone composed of octahedral magnesium aluminum oxide crystals. Spinel occurs in all colors, frequently resembling and being mistaken for rubies and sapphires.

Sugilite is semi-precious gemstone generally a medium to dark purple it can also range from pink to brown to black. It is usually opaque with a waxy luster and often has brown, pink and white inclusions, looking like a purple version of turquoise. It is usually polished and not faceted.

Sunstone is another name for aventurine.

~ T ~

Tanzanite is a rare, transparent, blue-violet type of zoisite resembling sapphire. It was discovered in the Merelani district of Tanzania, near Mount Kilimanjaro in 1967 and was renamed by the renowned jewelry store Tiffany & Co. All purple and blue varieties of the stone are the result of heat treatment. The stone is a yellowish-brown "bug juice" color when it is mined, but when heated to between 800-900 degrees Fahrenheit, it becomes that gorgeous violet blue that is used in jewelry.

Tiger's Eye is a type of microcrystalline chatoyant quartz that has replaced the asbestos mineral crocidolite to produce its unique appearance: Bands of a yellowish-brown to reddish-brown and when viewed from the opposite direction, the colors are reversed. It has a silky luster and is usually highly polished and set as a cabochon or cut as a bead to display the stone's chatoyancy.

Topaz is a very hard gemstone that is most commonly colorless, but colors include blue, pale green, and the spectrum of yellow through sherry orange to pink, and most unique, red. Blue topaz results from irradiation of clear topaz. Its the hardest of the silicate minerals, due to strong chemical bonds within the stone.

Tourmaline occurs as an elongate three-sided prism. It has the greatest color range of any gemstone, occurring in more than 100 colors. It is a dichroic gemstone and appears to have different colors depending on the angle at which it is seen. Lighter colors are considered more valuable than the darker. It ranges in color from pink to green to red (Rubellite) to purple to blue-green (Indicolite) to colorless (Achroite) to black. Watermelon tourmaline is both pink and green.

Tourmalinated Quartz is a variety of transparent quartz that has needle-like inclusions of black to dark green tourmaline crystals.

Tsavorite is a rare, deep green variety of grossular garnet discovered in 1967. It is one of the newest of the precious gemstones.  The emerald green color comes from vanadium and chromium. Tsavorite is similar to emerald, but is rarer and more durable and more refractive.

Turquoise is a non-translucent, porous semi-precious stone that is usually cut as a cabochon or as beads. The finest turquoise is robin's egg blue and has no matrix. North American turquoise is greener and has a matrix streaks. Over the years, oil from your skin is absorbed by the stone and it will change color slightly.

~ U-V-W ~

Unakite is a variety of granite that contains green epidote and pink feldspar but lacks mica giving it a green background with patches of red and pink.

Uvarovite is a rare green garnet with outstanding brilliance and color. Uvarovite is rarely cut as a gem because it almost never occurs in crystals large enough to be faceted.

Variscite is a relatively rare translucent pastel green to emerald green gemstone. Colors vary only slightly between yellow green to slightly darker greens and is often misidentified as turquoise. Its bright color comes from traces of chromium. It has a waxy luster and takes a fine polish.

~ X-Y-Z ~

Zircon comes in colors ranging from brown to reddish brown but other colors are possible. Contains trace amounts of the radioactive minerals hafnium, uranium and thorium. Over tens of thousands of years these radioactive components break down the lattice of the crystal leaving it with an amorphous structure and a dark pithy appearance. Zircons that are young and unaffected by radioactivity are termed "high" zircons and are transparent golden, yellowish-green and greenish-brown in color with incredibly high dispersion. "High" zircons can be heated to temperatures greater than 1800 degrees Fahrenheit and become colorless or blue and have often been used as a substitute for diamond.

Zoisite has three know forms of which Tanzanite is considered a gemstone. Other forms are anyolite, a green matrix containing rubies, and thulite, opaque pink crystals containing manganese.