Jewelry Information: Gemstones: Types and Information
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Following is a useful survey of popular gemstones, many of which are available here at  Use our search function (above, right) to find jewelry items containing the gemstone you search for.

There are, of course, many hundreds of gemstones, so the list below only represents a few of them.  Each stone is illustrated with the more commonly available colors (because many are available in multiple colors), with facts as to their geological origins, hardness (1 to 10 (hardest) on the Moh's scale) and relative weight (by specific gravity).  Please note that most natural gemstones, such as pearls, emeralds and rubies, contain natural inclusions and variations in color which are not seen in artificial stones.  These imperfections are the marks of their natural origin, and are typically more noticeable than in diamonds. Just because an emerald, for instance, is "natural", it does not necessarily mean that it is desirable--a highly flawed stone is simply ugly, no matter what its pedigree.   For this reason, many of the rarer gemstones are available today in Lab Created, or synthetic, form--these are actually grown in a laboratory environment and are the same chemical composition as natural stones, except that they are virtually flawless.  Lab Created is NOT the same as "imitation" gemstones, which are not the same chemical composition as the genuine gemstone.  And, even natural gemstones are routinely treated (with heat, radiation or chemicals) to enhance color or to reduce imperfections. offers jewelry with both Lab Created (synthetic) and quality natural stones--synthetic stones are always indicated in the product description.  For more information on gemstones, visit the GIA helper site, How to Buy a Gemstone, or the International Colored Gemstone Association site.

Types of Gemstones

Alexandrite: Rare, color-changing gemstone which appears grass green in daylight and raspberry red in artificial light, some with "cat's-eye" effect.  Available as synthetic.  Composition: beryllium aluminum oxide; hardness: 8.5.
Agate: Translucent, cryptocrystalline variety of quartz--a banded variety of chalcedony.  In addition to banded varieties, "feathered", "mossy" and "plumed" varieties are common. 
Amethyst: Transparent purple quartz, available in shades from light to dark purple, is also the February birthstone.  Available as synthetic.  Keep from high heat and strong direct sunlight.  Composition: silicon dioxide, hardness: 7.0.
Aquamarine: Member of beryl family, as is emerald, ranges from light blue to bluish green to deep blue and is the March birthstone.  Is commonly available in excellent clarity, unlike emerald.  Composition: beryllium aluminum silicate; hardness: 7.7. 
Aventurine:  A form of quartz, this gemstone is translucent, usually blue-green in color, and is infused with mica-like inclusions giving it a shimmering effect, termed aventurescence. It may also occurs in brown, orange, yellow, blue and gray.  Composition: silicon dioxide + fuschite; hardness: 6.5 
Carnelian:  From the chalcedony (quartz) family, ranges light brownish-red to deep red.  Carnelian owes its color to iron oxide. Composition: Silicon dioxide; hardness: 7.0.
Chalcedony: Semitransparent or translucent, this gemstone can be found in many colors and color combinations, the most common of which are white to gray, grayish-blue, or varying shades of brown.  Composition: Cryptocrystalline silicon dioxide; hardness: 6-7 
Citrine:  From the quartz family, ranges from lemon yellow to brownish amber, a plentiful gemstone, it is often made by heating pale amethyst. Composition: Silicon dioxide; hardness: 7.0.
Coral: From the sea, coral occurs in white, orange, red, pink and black. The Mediterraneian yields the best red coral, while black coral is sourced from Hawaii and Mexico. Usually cabochon cut, or simply mounted in its natural shape (believed to best preserve its reputed healing powers). Composition: calcium carbonate or conchiolin; hardness: 3.5.
Cubic Zirconia (CZ): Rare in natural occurrence, CZ has been synthetically produced in volume and multiple colors since the 1970's.  To the untrained eye, white CZ appears as a high-quality diamond, though it is 75% heavier, has more "fire" and is softer than diamond.  Composition:  zirconium oxide; hardness: 8.5.
Diamond: The king of gemstones, we list it here simply for comparison.  Diamond is pure carbon, with included imperfections of other captured minerals, and is the April birthstone.  Available as synthetic.  Composition: carbon; hardness: 10.
Emerald:  A "precious gem", Emerald is a member of the beryl family, very rare, and is the May birthstone.  Natural emeralds contain more flaws than most gems, tolerated because of its rarity.  Often oiled to hide flaws, emeralds should never be ultrasonically cleaned.  Available as synthetic.  Composition: beryllium aluminum silicate; hardness: 7.7. 
Garnet:  Available in almost any color range (greens (see Tsavorite), reds, yellows, oranges, color-changing), but most commonly seen it its deep red variety, some of which can be mistaken for ruby.  Rhodolite is raspberry to deep pinkish red, while Mozambique is slightly redder and darker.  January birthstone.  Composition: magnesium aluminum and iron aluminum silicate; hardness: 7. 
Hematite: The mineral form of iron oxide, it is found in colors ranging from black to steel-gray, and sometimes brown to red. It is harder than iron, but weakly magnetic.  Composition: iron oxide; hardness: 5.5-6.5 
Iolite: Transparent, deep blue to yellowish-gray, also called dichroite or cordierite, similar in color to sapphire but not as hard. Relatively new to jewelry.  Composition: magnesium aluminum silicate; hardness 7.3. 
Jade:  Two distinct minerals, both called Jade: jadeite (most valuable) and nephrite.  Jadeite is found in a wide range of colors--green, white/gray, mottled green/white, pink, brown, mauve, yellow, orange and lilac.  Nephrite jade is found in shades of green, from very dark (black jade) to pale.  Composition: Jadeite: sodium aluminum silicate; hardness: 7.0.  Nephrite: calcium magnesium iron silicate; hardness: 6.5. 
Jasper: An opaque variety of Quartz, jasper is found in red, green, brown and yellow colors, usually with veins and color vairiations. Believed in ancient cultures to bring rain and protection from poisonous venom. Composition: silicon dioxide; hardness: 7.0. 
Moonstone: A member of the feldspar family, it is transparent, milky white to blue, possessing an internal floating white or blue light, an optical effect known as adularescence. Composition: potassium aluminum silicate; hardness: 6-6.5. 
Onyx:  Straight-banded, semitranslucent-to-opaque quartz, found in reds, oranges, apricot, and browns--curved banded varieties are known as agate.  Composition: silicon dioxide; hardness: 7.0 
Opal: The October birthstone, it exhibits an intense display of many microscopic colors, due to light interference from included silica spheres.  Must be treated with care, avoid heat because some opals tend to dry out and crack, periodically soak in water for several hours.  Composition: hydrated silica gel; hardness: 5.5-6.5.  
Peridot:  Yellowish green to deep chartreuse, the August birthstone, peridot can chip and scratch easily.  Usually natural, it is not routinely treated for enhancement.  Composition: magnesium iron silicate; hardness: 6.5-7.0.
Quartz:  This mineral family contains gems representing every color, transparent to opaque: Citrine, Ametrine, Praseolite, Amethyst, Rose and Smokey Quartz, Agate, Chalcedony, Carnelian, Aventurine, Bloodstone, Cat's-eye, Chrysoprase, Jasper, Tiger's-eye and even Petrified Wood.  Composition: silicon dioxide; hardness: 7.0. 
Rhodonite: A glassy, pink-colored, mineral, named after the Greek word "rhodon" meaning "rose", with color varying from pink to redish pink to orange, often with black inclusions. It is found in Russia, Australia, Sweden, Brazil and US.  Composition: crystallized manganese inosilicate; hardness: 5.5-6.5.
Ruby: A "precious gem", ruby is the brilliant transparent red variety of the mineral corundum, ranging from purple/blue-red to yellowish red, the July birthstone and the "gem of gems".  Also translucent varieties with optical star effects.  Available in synthetics.  Composition: aluminum oxide; hardness: 9.0.
Ruby-Zoisite: This mineral is a naturally occurring combination of ruby and Tanzanite (zoisite) in the same stone.  Also known as anyolite, it was discovered in Tanzania in 1954.  Composition: calcium aluminum silicate; hardness: 6.5-7 
Sapphire: One of the "precious gems", sapphire is a variety of corundum, occurring in virtually every color--its red variety is known as the ruby.  Blue sapphire is the September birthstone.  Also seen in a translucent "star-effect" variety.  Available as synthetic.  Composition: aluminum oxide; hardness: 9.0 
Sodalite: Typically a royal-blue in color, sodalite's crystals are clear-to-translucent. Found in Ontario Canada, it also occurs in gray, green, yellow and pink colors.  Composition: Sodium plus oxidixed aluminum, silicon and chlorine; hardness: 5.5-6 
Spinel: One of the few gems not color-enhanced or treated, spinel occurs in red-orange (flame). orange-red, grayish- and greenish-blue, gray-green and purple to violet. Sometimes confused with more valuable gemstones such as ruby, emerald and sapphire.  Composition: magnesium aluminum oxide; hardness: 8.0.
Tanzanite:  A modern gemstone (since 1967), also known as Zoisite, it is transparent blue to purple blue.  Should be protected as it can chip easily.  Composition: calcium aluminum hydroxysilicate; hardness: 6.5. 
Tiger's Eye:  A variation of Quartz, Tiger's Eye is golden, yellowish brown/red color with depth which shows shimmering lines of light. When cut into a cabochon, it resembles an eye. A blue variety is called "Hawk's Eye".  Composition: silicon dioxide; hardness: 7.0.
Topaz:  This brilliant and heavy stone is often imitated with lesser value quartz (citrine), but genuine topaz is rare--it is the birthstone for November.  Topaz occurs in yellow thru orange-or pink-brown, as well as light red and the popular light to medium blue.  Composition: aluminum fluorohydroxysilicate; hardness: 8.0. 
Tourmaline:  A more recent gemstone, it is found in virtually every color, even within the same stone, though pink and green are the most common.  Composition: complex borosilicate; hardness: 7-7.5. 
Tsavorite:  Green garnet, more durable and vibrant than emerald, yet less costly.  Also appears as rarer demantoid garnet which is slightly softer with more brilliance.  Composition: calcium aluminum silicate; hardness: 7. 
Turquoise:  The December birthstone, "Turkish Stone" is prized in Asia and Africa for reputed healing and luck-attracting qualities. Opaque blue or blue-green, commonly sourced from Arizona, New Mexico and Mexico. Fades over time; can be damaged by soap and grease. Composition: hydrated copper aluminum phosphate; hardness: 6.0. 
Zircon:  A natural gemstone (not to be confused with cubic zirconia, CZ), zircon is a brilliant, transparent stone occurring as colorless to brown, yellow, orange, red, green and the popular blue. Brittle and prone to chipping, yet exhibits "fire" similar to diamond.  Composition: zirconium silicate; hardness: 6.5-7.5. 

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