Agate is a form of chalcedony quartz that forms in concentric layers in a remarkable variety of colors and textures.
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.
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.
Malachite is a copper carbonate with distinctive green veining. Though not a particularly hard stone, it takes an excellent polish.
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.
Mali Garnet, is one of the hybrid garnets, a mixture of grossular and andradite garnets. The name derives from the West African country of Mali where it was first discovered in 1994.
Almandine Garnet, the most common garnet, is dark brownish or purplish red. Garnet is very popular for its excellent hardness and brilliance.
Maw-sit-sit is one of the more unusual gemstones in the world. It was first discovered in 1963 and named after a village in northwestern Burma.
Amazonite is a gemstone variety of green microcline, a feldspar mineral. It is named after the Amazon river in Brazil., though no deposits have been found there.
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.
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.
Moonstone is a unique stone that reflects light in a distinctive shimmering phenomenon known as adularescence.
Amethyst is the most precious gemstone within the quartz group. Amethyst ranges in color from pale lilac to deep reddish purple.
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 .
Ametrine is a form of quartz which occurs in bands of yellow and purple, a combination of the colors of amethyst and citrine.
Moss opal is a milky white opal with unique inclusions of green hornblende in moss-like patterns.
Ammolite is a rare gemstone of organic origin that is fairly new to the market, with commercial mining beginning only in 1981.
Mystic Quartz is the product of a new high tech enhancement process applied to colorless quartz.
Andalusite is a strongly pleiochroic gem, which means that is has different colors when viewed from different directions.
Colorful Mystic Topaz is the product of a high tech enhancement process that is stable and permanent.
Supplies of andesine-labradorite are quite recent, with the mineral found in a range of colors, including red, yellow, champagne and green.
Nuumite is an opaque metamorphic rock with an iridescent play of color. Its chief constituent minerals are gedrite and anthophyllite, along with pyrite, pyrrhotine and chalcopyrite.
Apatite, a stone seldom found in jewelry stores, is beloved by collectors for its many different colors and forms.
Obsidian is a naturally occurring volcanic glass. It is formed when felsic lava extruded from a volcano cools without crystal growth.
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.
Onyx is the black form of chalcedony, a cryptocrystalline form of quartz.
Aventurine is a type of green quartz often used for carvings and cabochons.
More than any other gem, each opal is unique. No other stone has as rich and varied a folklore. Opals are also the most delicate gems commonly worn and require special care.
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 when polished.
An opal doublet consists of a slice of natural opal glued to a black backing, which causes the colour to become darker and more vibrant.
A new high tech enhancement process applied to colorless stones such as topaz has created a new variety we call Azotic Topaz, named after the company that invented the patented process.
Orthoclase is a transparent yellow feldspar resembling citrine quartz or yellow beryl, found primarily in Madagascar.
Beryl is one of the most important gem minerals. The most famous beryl is emerald, but other beryl varieties include aquamarine, heliodor and morganite.
Paraiba tourmaline is a rare copper-bearing gem with an exceptional neon blue color. First found in Brazil in 1989, similar material has since been found in Nigeria and Mozambique.
Bloodstone, also known as heliotrope, is a green gemstone dotted with bright red spots of iron oxide.
Peanut wood is a variety of petrified wood, where the shape and structure of the wood is preserved when the original organic material is replaced by quartz.
Boulder Opal is the second most prized form of opal, after black opal. The name derives from the fact that boulder opal is found embedded in ironstone boulders.
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.
Pure calcium carbonate is colorless, but calcite is often colored by various impurities, including iron, magnesium, manganese, zinc or cobalt.
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.
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 a 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 gems 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 or the cat's eye effect. Usually found in colors of 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. Rainbow moonstone is another variety of moonstone that adds multicolor to its mystical glow.
Scapolite is a sodium calcium aluminum silicate with a hardness of 5.5 to 6 on the Mohs scale. It is named from the Greek for "stick," since its crystals grow in columns.
Rhodochrosite is usually found in an aggregate form with alternating light and dark stripes in zigzag bands, somewhat similar in that respect to malachite or agate.
Tourmaline with tiny parallel inclusions sometimes display a strong cat's eye effect when polished.
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.
Chalcedony is the fine-grained variety of the silica mineral quartz. It has a waxy luster and appears in a great variety of colors.
Rhodonite is a manganese iron magnesium calcium silicate, and a member of the pyroxenoid group of minerals.
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.
The unique soft pink color of rose quartz is thought to derive from tiny traces of titanium impurities. Rose quartz crystals tend to be cloudy which deepens the color.
Chrome Diopside is colored by chromium and displays a rich forest green that has similarities to tsavorite garnet and chrome tourmaline.
Vivid pink to red tourmaline, often with a violet tinge, is known as rubellite. It is one of the most valuable tourmaline colors.
Chrome Diopside is colored by chromium and displays a rich forest green that has similarities to tsavorite garnet and chrome tourmaline.
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 make fine rubies so valuable.
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-Zoisite is the natural combination of ruby and zoisite crystals in a single specimen. Often used for carvings.
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.
Rutile Quartz is clear or smoky quartz with inclusions of rutile crystals.
Chrysocolla is a hydrous copper silicate. Often confused with turquoise, chrysocolla is found in unusual multicolor combinations as well as in blue or green.
Rutile Topaz is colorless topaz with inclusions that look like rutile crystals. But the inclusions are actually limonite staining in thin channels in the topaz.
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.
Sapphire, with its excellent hardness, second only to diamond, is one of the 4 traditional precious gemstones.
Named from the French word for lemon, citrine is yellow to gold to orange-brown shades of transparent quartz.
As a gemstone scapolite is not well known, but it can be a very attractive stone. Its color, which is usually a virbrant yellow to orange, pink or violet, is its best feature.
Clinohumite is a rare mineral and an especially rare gemstone. Only three sources of gem-quality material clinohumite are known, in Tajikistan, Siberia and Tanzania.
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.
Diaspore, sometimes marketed under the name Zultanite, is a color change gem from Turkey recently introduced to the international market.
Sillimanite is an aluminum silicate, related to both andalusite and kyanite. In fact these three minerals share the same chemical composition but different crystal structures.
Color-change Garnet is a mix of spessartite and pyrope garnet. This garnet presents a color change from brownish in daylight to a rose pink in incandescent light.
Smithsonite is one of two zinc-containing minerals discovered by the British mineralogist James Smithson. The zinc silicate was named smithsonite in his honor.
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.
Smoky quartz is fast becoming a designer favorite for its earthy tone and tribal look.
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.
Obsidian is a naturally occurring volcanic glass. In some stones, the inclusion of white crystals of cristobalite produce a blotchy pattern, known in as snowflake obsidian.
Danburite derives its name from Danbury, CT, where it was first discovered in 1839. It is quite hard, with a rating of 7 to 7.5 on the Mohs scale.
The mineral sodalite is named for its sodium content. As a gemstone, sodalite is usually blue, often with a violet tint, and frequently contains white veins of calcite.
Demantoid Garnet is the rarest and most valuable of the garnets. Found in green to emerald green, demantoid garnet is difficult to find and is typically found only in smaller sizes.
The most valuable spessartite garnets display a bright, orange red. The best specimens come from Namibia.
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.
Sphalerite is a rare collector's gem whose claim to fame is exceptional dispersion or fire. In fact its dispersion rating is three times as high as that for diamond.
Diamond, the hardest known natural material, is a transparent crystal of carbon. Diamond is famed not only for its superb hardness, but also for its high refractive index and dispersion.
Sphene is a brilliant yellowish-green, green or brown gemstone of high luster, unique color shades and, with brilliant cut, an intensive fire.
Dumortierite Quartz is an ususual quartz that is integrown with the mineral dumortierite. The inclusions of dumortierite give it a deep blue color that is unique in the world of quartz.
Due to its excellent hardness and clarity spinel is an excellent gemstone for all types of jewelery. Spinel is never treated in any way.
Emerald is the most precious stone in the beryl group. The wonderful green color of emerald is unparalleled in the gem world.
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.
Fire agate is an opaque, limonite-bearing chalcedony with an iridescence which is created by diffraction of light by the layered structure.
Diopside is best known for the vivid green chrome diopside, but the black diopside exhbiiting asterism or the star effect is also important.
Fire Opal is an unusual variety of opal from Mexico, with colors ranging from yellow to orange and orange-red. Some fire opals are clear enough for facets.
Star garnet is a rare and unsuual garnet, found only in Idado in the USA and in India. It displays a four-ray star due to aligned inclusions of rutile.
Fluorite is a mineral with a veritable bouquet of brilliant colors that range from purple to blue, green, yellow, colorless, brown, pink and orange.
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.
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.
Rose quartz displaying asterism or the star effect is rare. The unique soft pink color of rose quartz is thought to derive from tiny traces of titanium impurities.
A recent discovery (1966), Gaspeite is a very rare nickel carbonate mineral named for the place in eastern Canada where it was first described.
Star Ruby is a ruby which displays asterism, a six-rayed star that shimmers over the surface of the stone when it is moved.
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.
Star Sapphire is a sapphire which contains unusual tiny needle-like inclusions which produce a phenomenon called asterism.
Grossularite (or grossular) garnet is a calcium-aluminium garnet. The name grossular is derived from the botanical name for the gooseberry, grossularia.
Sunstone is a plagioclase feldspar with a unique glitter from platelets of hematite. Typically it has a red, more rarely a blue or green, glitter. Star sunstones are known but rare.
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.
Quartz with red inclusions of lepidocrosite, hematite or goethite is often sold under the name strawberry quartz.
Hematite, an iron oxide, is typically a blackish grey. When highly polished it can sometimes look like silver. Hematite is a remarkably dense material.
Sugilite is an obscure and quite rare mineral named after the Japanese geologist, Ken-ichi Sugi, who discovered it in 1944.
Hemimorphite is usually found in aggregate form with blue and white bands, or mixed with a dark matrix.
Sunstone is a type of plagioclase feldspar that exhibits a spangled appearance, due to reflections of red hematite.
Hessonite is an orange-brown variety of garnet colored by traces of manganese and iron. It is sometimes know as cinammon stone.
Tanzanite is a variety of zoisite. Colors range from blue to purple to green. The highly coveted color is the deep blue which shows a purple hue shimmering around it.
Hiddenite is a form of spodumene containing chromium. The green color varies from a yellowish to a bluish green.
Tashmarine Diopside is a brilliant yellow-green diopside from a recent discovery in Tajikistan, Uzbekistan and Western China.
Idocrase is also known as Vesuvianite, since it was originally found on the Mt. Vesuvias volcano. The color is normally green, but also can be brown, yellow, blue or purple.
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.
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 Matrix is the name given to a mineral aggregate in which tiger's-eye-like structures alternate with iron oxide layers.
Pleochroism is very pronounced in iolite and is seen as three different color shades in the same stone: violet blue, yellow gray and a light blue.
Topaz is an important gem due to its hardness and high refractive index. Topaz comes in many colors but the blue topaz is especially popular.
Jadeite is found in most colors from pure white thru pink, brown, red, orange, violet, blue, and black, to an range of greens.
One of the most versatile of gems, tourmaline is found in every color. It can show every tone from pastel to dark, and can appear in various colors in the same stone.
Jasper is usually considered a chalcedony, but scientists put it in a group by itself because of its grainy structure.
The green species of garnet was discovered in 1967 by British geologist Cambell R. Bridges in the bush along the frontier between Kenya and Tanzania.
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.
Turquoise, the blue cousin to 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.
Kyanite is a layered crystal with a luster that is vitreous to almost pearly, and is usually found in a sapphire-like blue.
Variscite is a relatively rare phosphate mineral and high quality specimens are used as gemstones and for carvings. Variscite is colored by traces of chromium .
Labradorite is a member of the plagioclase feldspar group and displays a distinctive schiller in lustrous metallic tints.
Verdite is a light to dark green serpentine rock which is often spotted or variegated. Most specimens come from South Africa and Zimbabwe.
Lapis lazuli has been used for thousands of years for jewelry and ornamental objects. The unique deep blue color has never lost its attraction.
Zircon has great brilliance and intensive fire, due to its high refractive index and strong dispersion.
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 is first discovered in 1974.
First Published: October-17-2007
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