Actinolite is a rare translucent variety of chatoyant actinolite. It is an amphibole silicate that is sometimes mistakenly called 'cat's eye jade'.
Malachite is copper carbonate with distinctive green veining. Though not a particularly hard stone, it takes an excellent polish.
Agate is a form of chalcedony quartz that forms in concentric layers in a remarkable variety of colors and textures.
Mali garnet, is one of the hybrid garnets, a mixture of grossular and andradite garnets. It gets its name from the African country where it was first discovered.
Agate is a form of chalcedony quartz that forms in concentric layers in a remarkable variety of colors and textures. Geodes are rock cavities or vugs with internal crystal formations.
Maw-sit-sit is an unusual gemstone. It was first discovered in 1963 and named after a village in Northwestern Burma.
Alexandrite is one of the rarest of all colored gemstones and is famed for its color change from green in daylight to red under incandescent light.
Melanite is the black variety of the rare andradite garnet. It is sometimes known as titanian andradite.
Almandine garnet, the most common garnet, is dark-brownish or purplish-red. Garnet is very popular for its excellent hardness and brilliance.
Moldavite is a bottle-green to brown-green gemstone belonging to the tektite group. It is formed from condensed rock vapors after a meteorite impact.
Amazonite is a gemstone variety of green microcline, a feldspar mineral. It is named after the Amazon river in Brazil, although no deposits have been found there.
Moonstone is a unique stone that reflects light in a distinctive shimmering phenomenon known as adularescence.
Amber, the fossilized, hardened resin of the pine tree, is one of the few gemstones of organic origin. Most amber is found in the Baltic, where it formed about 50 million years ago.
The pink form of beryl was named morganite, after the American banker and collector J.P. Morgan. A soft pink to violet, morganite belongs to the same family as emerald.
Amethyst is the most precious gemstone within the quartz group. Amethyst ranges in color from pale lilac to deep reddish-purple.
Moss opal is a milky white opal with unique inclusions of green hornblende in moss-like patterns.
Ametrine is a form of quartz that occurs in bands of yellow and purple, a combination of the colors of amethyst and citrine.
Mystic quartz is the product of a new high tech enhancement process, whereby a coating is applied to colorless quartz.
Ammolite is a rare gemstone of organic origin that is fairly new to the market, with commercial mining beginning only in 1981.
Colorful mystic topaz is the product of a high tech enhancement process that is stable and permanent.
Andalusite is a strongly pleochroic gem, which means that it can display different colors when viewed from different angles.
Nuummite is an opaque metamorphic rock with an iridescent play of color. Its chief constituent minerals are gedrite and anthophyllite.
Supplies of andesine-labradorite are quite recent, with the mineral found in a range of colors, including red, yellow, champagne and green.
Obsidian is naturally occurring volcanic glass. It is formed when felsic lava extruded from a volcano cools without crystal growth.
Apatite, a stone seldom found in jewelry stores, is beloved by collectors for its many different colors and forms.
Onyx is the black form of chalcedony, a cryptocrystalline form of quartz.
Aquamarine is best known for its breathtaking range of blue colors and belongs to the same family as emerald (beryl). Aquamarine is colored by trace amounts of iron.
More than any other gem, each opal is unique. No other stone has such rich and varied folklore. Opals are also the most delicate gems commonly worn.
Aventurine is a type of green quartz often used for carvings and cabochons.
An opal doublet consists of a slice of natural opal glued to a black backing, which causes the color to become more vibrant.
Axinite is a group of brown to violet-brown or reddish-brown minerals that sometimes occur in gem quality. Axinite is distinctive for its strong vitreous luster.
Orthoclase is a transparent yellow feldspar resembling citrine quartz or yellow beryl, found primarily in Madagascar.
A new high tech enhancement process using thin film deposition has created this new-look topaz.
Paraiba tourmaline is a rare copper-bearing gem with a vivid neon blue color. First found in Brazil in 1989, similar material has since been found in Africa.
Beryl is one of the most important gem minerals. The most famous beryl is emerald, but other beryl varieties include aquamarine, heliodor and morganite.
Peanut wood is a variety of petrified wood, where the shape and structure of the wood is pre- served when the original organic material is replaced by quartz.
Bloodstone, also known as heliotrope, is a green gemstone dotted with bright red spots of iron oxide.
Pearls are products of bivalve mollusks (mainly oysters and mussels). They are built up of nacre, which is mainly calcium carbonate in the form of aragonite crystals.
Boulder opal is the second most prized form of opal, after black opal. The name is derived from the fact that boulder opal is found embedded in ironstone boulders.
Peridot belongs to the forsterite-fayalite mineral series. It is an idiochromatic gem, meaning its color comes from the basic chemical composition of the mineral itself, rather than impurities.
Pure calcium carbonate is colorless, but calcite is often colored by various impurities, including iron, magnesium, manganese, zinc or cobalt.
Pietersite is a breccia aggregate of hawk's eye and tiger's eye, with swirling colors of blue, rusty red, gold and brown.
Carnelian is a brownish red to orange variety of chalcedony quartz, colored by trace amounts of iron. Darker colors (red-brown to brown) are often referred to by the name sard.
Prehnite, a form of calcium aluminum silicate, has a vitreous mother-of-pearl luster. Affordably priced for its size, prehnite makes distinctive and interesting jewelry.
Cassiterite is one of the densest gem materials known. It also has a very high refractive index, higher than zircon, sphene and demantoid garnet.
Pyrope garnet is the most famous of the red garnets. Its dark, blood red color often resembles the color of ruby.
Chatoyancy, (the cat's eye effect), is the reflection of light by parallel fibers, needles, or channels, which resemble the slit eye of a cat.
Quartz is one of the most common minerals on earth and is well known in the gemstone world in its many forms including amethyst, citrine and ametrine.
Aquamarine is best known for its breathtaking range of blue colors and belongs to the same family as emerald. Cat's eye aquamarine is quite rare.
Quartz cat's eye is quartz in which inclusions of rutile create chatoyancy (the cat's eye effect). Usually found in white, green, yellow or brown.
Diaspore, sometimes marketed under the name zultanite, is a color change gem from Turkey. Cat's eye diaspore is fairly rare.
A combination of orthoclase and albite arranged in layers cause the lovely sheen. Despite the name, rainbow moonstone is actually a variety of labradorite with a multicolored adularescence.
Scapolite is a sodium calcium aluminum silicate with a hardness of 5.5 to 6 on the Mohs scale. It is named after the Greek word for "stick", since its crystals grow in columns.
Rainbow pyrite is a recent find from Russia. The material comes in the form of druzy - a layer of miniature pyrite crystals coating a matrix.
Tourmaline with tiny parallel inclusions sometimes displays a strong cat's eye effect when polished.
Rhodochrosite is usually found in an aggregate form with alternating light and dark stripes in zigzag bands.
Chalcedony is the fine-grained variety of the silica mineral quartz. It has a waxy luster and appears in a great variety of colors.
Rhodolite garnet is the name applied to a mixture of pyrope and almandite. Rhodolite tends to be lighter in color than most other kinds of red garnet.
Charoite is a new gem on the market, first appearing in 1978. It is found only in one location in Siberia, Russia. The swirling shapes of lavender and violet are quite unique.
Rhodonite is a manganese iron magnesium calcium silicate, and a member of the pyroxenoid group of minerals.
Chrome diopside is colored by chromium and displays a rich forest green that has similarities to tsavorite garnet and chrome tourmaline.
The unique soft pink color of rose quartz is thought to be derived from tiny traces of titanium. Rose quartz crystals tend to be cloudy, which deepens its color.
Chrome tourmaline is a distinct variety of tourmaline colored by chromium. It is sometimes referred to as chrome dravite and is known for its rich forest green color.
Vivid pink to red tourmaline, often with a violet tinge, is known as rubellite. It is one of the most valuable tourmaline colors.
Faceted chrysoberyl is a beautiful gem which is not as well known as it deserves. Apart from the very good hardness (8.5 on the Mohs scale), it has excellent luster.
Ruby is the red variety of corundum, the 2nd hardest substance on the Mohs scale, with a rating of 9. It is the combination of hardness and rich color that makes fine ruby so valuable.
The most famous and valuable cat's eye gemstone is chrysoberyl cat's eye. It is valued for its excellent hardness (8.5) and sharp cat's eye.
Ruby-in-fuchsite is a natural combination of ruby and fuchsite in the same specimen. It is an interesting and colorful stone, with blue to emerald-green fuchsite and pink, purple or red ruby inclusions.
Chrysocolla is hydrous copper silicate. Often confused with turquoise, chrysocolla is found in unusual multicolor combinations as well as blue or green.
Ruby-zoisite is the natural combination of ruby and zoisite crystals in a single specimen. It is often used for carvings.
Chrysoprase is a gemstone variety of chalcedony or cryptocrystalline quartz, colored by trace amounts of nickel. Its color varies from apple-green to deep green.
Rutile quartz is clear or smoky quartz with inclusions of rutile crystals.
Named after the French word for lemon, citrine is yellow, gold or orange-brown transparent quartz.
Rutile topaz is colorless topaz with inclusions that look like rutile crystals. But the inclusions are actually thin channels of limonite staining.
Clinohumite is a rare mineral and an especially rare gemstone. Only three sources of gem-quality clinohumite material are known; in Tajikistan, Siberia and Tanzania.
Sapphire, with its excellent hardness, second only to diamond, is one of the four traditional precious gemstones.
Diaspore, sometimes marketed under the name zultanite, is a color change gem from Turkey, which was recently introduced to the international market.
As a gemstone scapolite is not well known, but it can be a very attractive stone. Its color, which is usually a vibrant yellow, orange, pink or violet, is its best feature.
Color-change garnet is a mix of spessartite and pyrope garnet. This garnet presents a color change from brownish in daylight to rose pink in incandescent light.
Seraphinite is a trade name for a particular form of clinochlore. The dark-green color of seraphinite is enhanced by a silvery and feathery shimmer caused by mica inclusions.
Some rare sapphires exhibit a color change under varying lighting conditions. Color change sapphires are typically blue in natural light and purple under incandescent light.
Serpentine is a type of green magnesium silicate aggregate. It is used as a decorative stone or for carvings.
Precious coral is a species of coral that grows in rocky seabottoms. Coral exhibits a range of warm reddish-pink colors ranging from salmon pink to deep-red.
Sillimanite is a type of aluminum silicate that is related to both andalusite and kyanite. In fact, these three minerals share the same chemical composition but have different crystal structures.
Danburite gets its name from Danbury, Connecticut, where it was first discovered in 1839. It is quite hard, with a rating of 7 to 7.5 on the Mohs scale.
Smithsonite is one of two zinc-containing minerals discovered by the British mineralogist James Smithson. The zinc silicate was named smithsonite in his honor.
Demantoid garnet is the rarest and most valuable of the garnets. Found in green to emerald green, demantoid garnet is scarce and is typically only seen in small sizes.
Smoky quartz is fast becoming a designer favorite for its earthy tone and tribal look. It is one of the few gemstones that is gray or brown.
Dendritic agate is a whitish-gray or colorless chalcedony with fern-like inclusions known as dendrites. The inclusions look like plant material, but they are actually iron or manganese.
Obsidian is a naturally occurring volcanic glass. In some stones, the inclusion of white crystals of cristobalite produce a blotchy pattern, known as snowflake obsidian.
Diamond, the hardest known natural material, is a transparent carbon crystal. Diamond is famed not only for its superb hardness, but also for its high refractive index and dispersion.
The mineral sodalite gets its name from its sodium content. As a gemstone, sodalite is usually blue, often with a violet tint, and frequently contains white veins of calcite.
Dumortierite quartz is an unusual quartz that is intergrown with the mineral dumortierite. The inclusions of dumortierite give it a deep blue color that is unique in the world of quartz.
The most valuable spessartite garnets display a bright, orange-red. The best specimens come from Namibia.
Emerald is the most precious stone in the beryl group. The wonderful green color of emerald is unparalleled in the gem world.
Sphalerite is a rare collector's gem which has exceptional dispersion (also known as fire). In fact its dispersion rating is three times as high as that for diamond.
Enstatite is a rare gemstone that belongs to the pyroxene group of minerals. It is typically brown-green with a vitreous luster and is a collector's gem.
Sphene is a brilliant yellowish-green, green or brown gemstone of high luster, unique color shades and, with brilliant cut, an intense fire.
Fire agate is a type of opaque, limonite-bearing chalcedony with an iridescence caused by the diffraction of light in its layered structure.
Due to its excellent hardness and clarity, spinel is an excellent gemstone for all types of jewelery. Spinel is never treated in any way.
Fire opal is an unusual variety of opal from Mexico, which can be yellow, orange or orange-red. Some fire opal gemstones are clear enough for facets.
Spodumene is a relatively new mineral to science, with gem varieties discovered only in the last 120 years. Spodumene occurs in white, gray, pink, lilac and green.
Fluorite is a mineral with a veritable plethora of brilliant colors that include purple, blue, green, yellow, colorless, brown, pink and orange.
Diopside is best known for the vivid green chrome diopside, but the black diopside exhibiting asterism (also known as the star effect) is also important.
Fossil coral is a decorative material that is formed when ancient coral is gradually replaced with agate. The proper name for this material is agatized coral.
Star garnet is a rare and unusual garnet, found only in Idado in the USA and India. It displays a four-rayed star due to aligned inclusions of rutile.
A recent discovery (1966), gaspeite is a very rare nickel carbonate mineral named after the place in Eastern Canada where it was first described.
Star lemon quartz is a lemon-yellow variety of quartz that displays asterism (the star effect).
The colorless precious beryl is known as goshenite. It is named after the small town of Goshen in Western Massachusetts where it was first described.
Moonstone is a combination of orthoclase and albite arranged in layers which cause the lovely sheen. Star moonstone exhibits a stunning cat's eye or four-rayed star effect.
Grossularite (or grossular) garnet is a calcium-aluminium garnet. The name grossular is derived from the botanical name for the gooseberry, grossularia.
Rose quartz displaying asterism or the star effect is rare. The unique soft pink color of rose quartz is thought to be caused by tiny traces of titanium.
Hackmanite exhibits an unusual phenomenon known as reversible photochromism, where a mineral changes color when exposed to sunlight.
Star ruby is a ruby that displays asterism, a six-rayed star that shimmers over the surface of the stone when it is moved.
Hambergite is one of the lesser-known gemstones. It is usually nearly colorless, with the vitreous luster of glass when cut. It is quite a hard material, with a hardness of 7.5.
Star sapphire is a sapphire that contains unusual tiny needle-like inclusions. These needles produce a phenomenon called asterism.
Hematite is iron oxide that is typically blackish-gray. When highly polished it can sometimes look like silver. Hematite is a remarkably dense material.
Sunstone is plagioclase feldspar with a unique glitter from platelets of hematite. Typically it has a red glitter, and more rarely a blue or green glitter. Star sunstones are known but rare.
Hemimorphite is usually found in aggregate form with blue and white bands, or mixed with a dark matrix.
Quartz with red inclusions of lepidocrosite, hematite or goethite is often sold under the name strawberry quartz.
Hessonite is an orange-brown variety of garnet colored by traces of manganese and iron. It is sometimes known as cinammon stone.
Sugilite is an obscure and quite rare mineral named after the Japanese geologist, Ken-ichi Sugi, who discovered it in 1944.
Hiddenite is a form of spodumene containing chromium. The green color varies from a yellowish to a bluish-green.
Sunstone is a type of plagioclase feldspar that exhibits a spangled appearance, due to reflections of red hematite.
Howlite is an interesting grayish-white mineral that is sometimes referred to as white turquoise because of its distinctive veining.
Tanzanite is a variety of zoisite. Colors of tanzanite include blue, purple and green. The highly coveted color is deep blue, which has a purple pleochroism.
Idocrase is also known as vesuvianite, since it was originally found on Mt. Vesuvias. The color is normally green, but it can also be brown, yellow, blue or purple.
Tashmarine diopside is a brilliant yellow-green diopside from a recent discovery in Tajikistan, Uzbekistan and Western China.
The most sought after of all natural topaz is called imperial topaz. Its rich golden color with reddish and orange overtones is generally not enhanced by any kind of treatment.
Tiger's eye is a type of opaque macrocrystalline quartz with a fibrous structure. It typically displays chatoyant stripes, because structural fibers are crooked or bent.
Pleochroism is very pronounced in iolite and is seen as three different color shades in the same stone; violet, yellow-gray and blue.
Tiger's eye matrix is the name given to tiger's eye that is cut and finished with some of its host rock intact.
Jadeite is found in most colors, including pure white, pink, brown, red, orange, violet, blue, black and a range of greens.
Topaz is an important gem due to its hardness and high refractive index. Topaz comes in many colors and blue topaz is especially popular.
Jasper is usually considered a type of chalcedony, however, scientists put it in a group by itself because of its grainy structure.
Tremolite is a rare gemstone sometimes known as 'hexagonite' or 'tremolite-hexagonite'.
Kornerupine is a rare transparent to translucent, typically brownish-green collector's gem. It was named after Danish naturalist, artist and explorer, Andreas Nikolaus Kornerup.
One of the most versatile of gems, tourmaline is found in every color. It can show every tone from pastel to dark, and can display various colors in the same stone.
Kunzite is the pale pink-violet to light-violet species of the mineral spodumene. Kunzite is named in honor of the mineralogist George F. Kunz.
This green species of garnet was discovered in 1967 by British geologist Campbell R. Bridges in the bush along the frontier between Kenya and Tanzania.
Kyanite is a layered crystal with a vitreous to almost pearly luster that is usually found in a sapphire-like blue color.
Turquoise, the blue cousin of lapis lazuli, has been known and valued for thousands of years. The early mines in Sinai, Egypt, were already worked out in 2000 B.C.
Labradorite is a member of the plagioclase feldspar group and displays a distinctive schiller in lustrous metallic tints.
Variscite is a relatively rare type of phosphate mineral. High quality specimens are used as gemstones and for carvings. Variscite is colored by traces of chromium.
Lapis lazuli has been used for thousands of years in jewelry and ornamental objects. The unique deep blue color has never lost its attraction.
Verdite is light to dark-green serpentine rock that is often spotted or variegated. Most specimens come from South Africa and Zimbabwe.
The blue variety of pectolite has become known as Larimar. A very rare mineral, it has only been found in the Dominican Republic, where it was first discovered in 1974.
Zircon has great brilliance and intensive fire, due to its high refractive index and strong dispersion.
Lepidolite is a lilac-gray or rose-colored lithium-bearing mineral of the mica group. It is one of the major sources of the rare alkali metals rubidium and caesium.
- First Published: October-17-2007
- Last Updated: July-29-2014
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