Gem Guide


Hardness: 7.0
Description: Agate is a microcrystalline variety of quartz (silica), chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks but can be common in certain metamorphic rocks. Colorful agates and other chalcedonies were obtained over 3,000 years ago from the Achates River, now called Dirillo, in Sicily.


Hardness: 8.5
Description: Alexandrite changes from green to red, mauve or brown in incandescent light. There are many many synthetic alexandrites on the market. Natural alexandrite is very rare. Alexandrite is found in Brazil, Madagascar, Myanmar, Russia, Sri Lanka and Zimbabwe. Alexandrite is a variety of chrysoberyl that displays a color change (alexandrite effect) dependent upon light. Alexandrite results from small scale replacement of aluminium by chromium oxide, resulting in alexandrite's characteristic green to red color change. Alexandrite from the Ural Mountains in Russia is green by daylight and red by incandescent light. Other varieties of alexandrite are yellowish or pink in daylight and a columbine or raspberry red by incandescent light. The ideal color change is fine emerald green to fine purplish red. Because of their rarity and the color change capability, "ideal" alexandrite gems are some of the most rare and expensive in the world.


Hardness: 7.0
Description: Amethyst is purple quartz and is one of the most popular gemstones. It varies from pale lavender to deep purple with red highlights. Amethyst is generally abundant and quite inexpensive. Amethyst is purple, lilac or mauve. The highest quality is transparent. The ancient greeks believed that Amethyst protected its owner from drunkenness. They wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.


Hardness: 7.0
Description: Aquamarine is light blue, blue-green and dark blue. The highest quality is transparent and is a gemstone-quality transparent variety of beryl closely related to the emerald. Aquamarine often pales if left out in the sun. Since the Dark Ages people thought that it could magically overcome the effects of poison. Sailors traveled with the crystals, believing that it would ensure a safe voyage, and guarantee a safe return. They also believed the mermaid's lower body was made of aquamarine.


Hardness: 6.5 - 7.0
Description: Bloodstone is usually green jasper with inclusions of red jasper. Sometimes yellow and/or other colors are also present. These multi-colored gemstones are called "fancy jasper". The red inclusions are supposed to resemble spots of blood, hence the name "bloodstone". The primary source of the stone is India. It is also found in Brazil, China, Australia, and the United States.


Hardness: 7.0
Description: Carnelian beads (other variants of the name include Carnelian beads, sadoine, Mecca stone, and pigeon's blood agate) are a gemstone jewelry made of carnelian quartz. The mineral is found worldwide, with India reputed for the best gemstones. Beads are made by heating and shaping agate several times, resulting in a change of color. Collections of beads have been found stored in pots dating to circa 1800 B.C.


Hardness: 8.5
Description: Translucent yellowish chatoyant chrysoberyl is called cymophane or cat's eye. Cymophane has its derivation also from the Greek words meaning 'wave' and 'appearance', in reference to the chatoyancy sometimes exhibited.
Although other minerals such as tourmaline, scapolite, corundum, spinel and quartz can form "cat's eye" stones similar in appearance to cymophane, the jewelry industry designates these stones as "quartz cat's eyes", or "ruby cat's eyes" and only chrysoberyl can be referred to as "cat's eye" with no other designation. Cat's eye material is found as a small percentage of the overall chrysoberyl production wherever chrysoberyl is found.


Hardness: 7.0
Description: Citrine is yellow to brown quartz with ferric impurities and rarely found naturally. It varies from pale yellow to rich golden yellow to dark orange. Although citrine may occur naturally, much is produced by heating amethyst or smoky quartz under controlled conditions. Darker colors are more highly prized, including medium golden orange ("Rio Grande" citrine) and dark sherry-colored ("Madeira" citrine). Brazil is the leading producer of citrine. It is nearly impossible to tell cut citrine from yellow topaz visibly.


Hardness: 10
Description: Diamonds are slightly yellowish, and in this general color range, those most approaching absolute lack of color are most prized. However, brightly colored diamonds are much rarer and more expensive. The deep blue Hope diamond and blue Eugenie diamond, both in the Smithsonian collection, are among the most famous examples. Diamonds are renowned as a material with superlative physical qualities. The name diamond is derived from the ancient Greek (adámas) which means unbreakable, They have been treasured since their use as religious icons in ancient India. The diamond's usage in engraving tools also dates to earliest human history. Many diamonds come from central and southern Africa. Also diamonds have been discovered in Canada, India, Russia, Brazil, and Australia.


Hardness: 7.5
Description: Emeralds are medium to dark green beryl which derives its color from chromium and vanadium. Emerald of fine color and clarity can be quite expensive. Almost all emeralds contain numerous small inclusions and fractures that promote fragility. Most stones on the market are impregnated with oils, waxes, or other substances to mask the fractures and sometimes enhance color. Emeralds in antiquity were mined by the Egyptians, in Austria and northern Pakistan. A rare type of emerald known as a trapiche emerald is occasionally found in the mines of Colombia. The best known sources include Colombia and Zambia. Fine emeralds are also found in other countries such as Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. In north America emeralds can be found in North Carolina and were also discovered in the Yukon.


Hardness: 7.0 - 7.5
Description: The garnet varieties occur in shades of green, red, yellow, orange, dark brownish to purplish red usually cut in small sizes (under 2 carats), as larger stones appear black. Garnet ranges in color from colorless to black though it is often thought of as only red. Garnets have been used since the Bronze Age as gemstones and abrasives. Six common species of garnet are recognized based on their chemical composition. They are pyrope, almandine, spessartite, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite.


Hardness: 7.0 - 7.5
Description: Transparent iolite (or Cordierite) is often used as a gemstone. The name "iolite" derives from the word violet in Greek. Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It is sometimes called "water-sapphire" and "Vikings' Compass" (It has an ability to determine the sun's direction on overcast days.) Iolite varies in color from sapphire blue to blue violet to yellowish gray to light blue as the light angle changes.
Iolite is sometimes used as an inexpensive substitute for sapphire. It is less expensive as it is softer than sapphires and can be found in Sri Lanka, India, Burma, Australia's Northern Territory, Namibia, Brazil, Tanzania, Madagascar, Connecticut, and the Yellowknife area of the Northwest Territories of Canada.


Hardness: 6.5 - 7.0
Description: There are two types of Jade: Jadeite and Nephrite. Jadeite is rarer and the highest quality is known as imperial Jade. Jadeite comes in many colors: red, yellow, green, lilac, black, orange, white, pink, blue and brown. Nephrite Jade is harder, more common and is often used in Chinese carvings. Nephrite Jade comes in various tones of green -- mostly with an olive green tone. The word 'jade' originates from the Spanish piedra de ijada or 'loin stone', from its reputation for curing ailments of the loins and kidneys. The earliest known jade artifacts from prehistoric sites are ornaments with bead, button, and tubular shapes. Additionally, it was used for axe heads, knives, and other weapons. When metal became available, the beauty of jade made it more valuable for ornaments and decorative objects. As early as 6000 BC Jade has been mined. Jade is the official gemstone of British Columbia, Alaska and Wyoming.


Hardness: 6.5 - 7.0
Description: Jasper is an opaque, impure variety of silica, usually red, yellow or brown in color. Jasper is used for ornamentation or as a gemstone. It can be highly polished and is used for vases, seals and snuff boxes. Jasper was a favorite gem in the ancient world. Its name can be traced back in Hebrew, Assyrian, Persian, Greek and Latin. On Crete jasper was used to produce seals circa 1800 BC at the palace of Knossos.


Hardness: 5.0 - 5.5
Description: In ancient Egypt lapis lazuli was a favorite for amulets and ornaments. It was also used by the Assyrians and Babylonians. Lapis jewelry was uncovered at excavations of the Predynastic Egyptian site Naqada (3300–3100 BC), and powdered lapis was used by Cleopatra as eyeshadow.
In ancient times, lapis lazuli was known as sapphire, which is now what the blue corundum variety is called. It was the sapphire of ancient writers because Pliny refers to sapphirus as sprinkled with specks of gold.
The Romans believed that lapis was an aphrodisiac. In the Middle Ages, lapis was used to keep the limbs healthy, as it was believed to have medicinal properties. Lapis was ground down, blended with milk and applied to boils and ulcers.


Hardness: 3.5 - 4.0
Description: Malachite is also known as "copper carbonate". Large quantities of malachite are mined in the Urals. It is found in the Congo, Zambia, Tsumeb, Namibia, Ural mountains, Russia, Mexico, England, and in the Southwestern United States especially in Arkansas and Arizona. In Israel, malachite is extensively mined at Timna valley, often called King Solomon's Mines. Archeological evidence indicates that the mineral has been mined and smelted at the site for over 3,000 years.


Hardness: 9.25
Description: Moissanite is the rare mineral form of silicon carbide (SiC) which has been found in meteorites and in mantle derived igneous rocks. Moissanite, in its natural form, is more rare than diamond. It is often referred to as "the other diamond".


Hardness: 6.0 - 6.25
Description: The most common moonstone is of the mineral adularia. Its name is derived from a visual effect caused by light reflecting internally from layer inclusion of different feldspars. Moonstone is found in many places like the European Alps, Brazil, India, Mexico, Myanmar, Madagascar; the USA, specifically Pennsylvania and Virginia; and Tanzania. However, it is Sri Lanka that produces the highest quality moonstones.


Hardness: 7.0
Description: Onyx is a rich-looking, affordable black stone. It is often mixed with pearls to create elegant jewelry. Onyx, sard, and sardonyx are all varieties of chalcedony (microcrystaline quartz). Onyx comes in brown, white, grey, and black. Sard is a reddish-brown variety. Sardonyx is a blend of sard and onyx with the red bands of sard and the white bands of onyx. If onyx is cleaned with an ultrasonic device or cleaned with abrasive or ammonia based chemicals, discoloration of the stone may occur. Onyx was known to the ancient Greeks and Romans. Use of sardonyx appears in the art of Minoan Crete at Knossos. Egyptians used onyx early as 3000 BC to make bowls and other pottery items.


Hardness: 6.0 - 6.5
Description: Opal in large sizes are rare and costly, especially black opal. Opals are sually cut as cabochons and beads. Occasionally they are found as fossilized (opalized) clamshells, snail shells, or wood. Transparent opals, such as Mexican red or orange fire opal, are often faceted. Values are normally determined by the presence and nature of color flashes. In the Middle Ages, opal was believed to provide great luck because it possessed all the virtues of each gemstone whose color was represented. The opal is the official gemstone for Australia and Nevada.


Hardness: 3.0
Description: Pearls are formed in shellfish, as a protective reaction to irritants such as sand. Cultured pearls are created by adding a substance like a piece of mussel or shell inside of an oyster of mussel. This then creates a pearl as inside layers of the shell grow over the substance. The price of pearls vary widely as a result of luster, shape, size, how they are grown, color and type. Natural pearls are more expensive than the cultured ones. Fresh water pearls are usually less expensive. Pearls are white, brown, silver, cream, black or pink depending on the type of shellfish and water. For thousands of years, most seawater pearls were collected by divers in the Indian Ocean, Persian Gulf, Red Sea, and Gulf of Mannar. The chinese hunted extensively for seawater pearls in the South China Sea. Today, most pearls used for jewelry are cultured.


Hardness: 6.5
Description: Peridot is gem-quality forsteritic olivine. Olivine is a very abundant, but gem quality peridot is rather rare. Peridot is a transparent lime to olive green. Peridot is one of the few gemstones that occur in only one color (green), with the most valuable being a dark-olive green color. Peridot has been found in Pallasite meteorites and except for moissanite is the only gemstone that has ever been collected from meteorites. Peridot olivine is mined in North Carolina, Arizona, Hawaii, Nevada, New Mexico, Mexico, Australia, Brazil, China, Myanmar (Burma), Norway, Pakistan, South Africa, Kenya, Saudi Arabia, Sri Lanka, and Tanzania. Avoid large temperature changes (such as leaving it be a heater vent or in a hot car). Do not clean peridot in a home ultrasonic cleaner.


Hardness: 9.0
Description: Ruby is gem quality corundum that may be any color of red depending on the chromium and iron content of the stone. Generally, ruby is quite durable. Still, rubies are subject to chipping and fractures if handled roughly. Rubies are found worldwide. The finest stones are from Myanmar. Bright red stones are mined in: Afganistan, Pakistan, Vietnam. Brownish-red rubies are from Thailand. Darker stones are generally produced from the mines in Australia, India, Russia and USA (Georgia, North Carolina, Wyoming, Montana, North Carolina, and South Carolina.). Recently ruby deposits have been discovered in Greenland. Prices are determined by color. The brightest red rubies called pigeon blood red, are more valuable than other rubies of similar quality. Red spinel is often mistaken as rubies by people lacking experience. Fine red spinels may approach the average ruby in value.


Hardness: 9.0
Description: All gem quality corundum that is not red ruby is considered sapphire such as blue, orange, yellow, violet, green, white and pink. Unless a color is stated, sapphire is normally blue. Color change sapphires will change between blue and violet depending on the light. Sapphires and rubies are often found together in the same area, but one gem is usually more abundant. Sapphire deposits are in Eastern Australia, Thailand, Sri Lanka, Madagascar, East Africa and in the United States at various locations (Gem Mountain) and in the Missouri River near Helena, Montana. Sapphires are quite durable, but are still subject to chipping and fractures if handled roughly.


Hardness: 7.0
Description: Sardonyx is a variant of onyx in which the colored bands are red rather than black.


Hardness: 8.5
Description: The transparent red spinels were called spinel-rubies or balas-rubies. In the past, before the arrival of modern science, spinels and rubies were equaly known as rubies.
Some spinels are among the most famous gemstones: Among them is the Black Prince's Ruby and the 'Timur ruby' in the British Crown Jewels, and the "cote de Bretagne" formerly from the French Crown jewels. The Samarian Spinel is the largest known spinel in the world, weighing 500 carats.
True spinel has long been found in the gemstone-bearing gravel of Sri Lanka and in limestones of the Badakshan province in nowadays Tajikistan and of Mogok in Burma. Recently gem quality spinels were also found in the marbles of Luc Yen (Vietnam), Mahenge and Matombo (Tanzania), Tsavo (Kenya) and in the gravels of Tunduru (Tanzania) and Ilakaka (Madagascar).


Hardness: 6.0 - 7.2
Description: Sunstone is not common, the best-known locality being Tvedestrand, near Arendal, in Norway. Sunstones occur embedded in a vein of quartz. It is found also near Lake Baikal, in Siberia, and in the United States, Pennsylvania, Lakeview, Oregon and at Statesville, North Carolina.


Hardness: 6.5
Description: Tanzanite may be blue, purple or slate gray. Tanzanite is rarer than diamonds with only one mine source in the world. It was discovered in northern Tanzania in 1967 and is a variety of the mineral zoisite. A synthetic version of tanzanite is called tanzanique. Tanzanite is often heat treated to improve its color and clarity. Tanzanite can easily be scratched or chipped. Clean your Tanzanite with warm, soapy water and a soft bristle brush. Avoid using ultrasonic cleaning.


Hardness: 9.0
Description: Topaz comes in many colors such as blue, yellow, pink, brown, green and clear. Imperial (orange-red) topaz is rare. Blue topaz is the most common and is the Texas state gemstone. In the Middle Ages the name Topaz referred to any yellow gemstone. Mystic topaz is colorless topaz with a thin film coating giving it a r ainbow effect and is not a naturally occurring topaz. Topaz can be found in the Ilmen and Ural mountains, Afghanistan, Czech Republic, Italy, Sweden, Germany, Norway, Sri Lanka, Pakistan, Japan, Mexico, Brazil, Flinders Island and the United States.


Hardness: 7.5
Description: Tourmaline comes in many colors such as blue, black, yellow, pink, red, green and clear. Tourmaline is a semi-precious stone that comes in a wide variety of colors. Great quantities of brightly colored Sri Lankan gem tourmalines were brought to Europe by the Dutch East India Company. The most common species of tourmaline is schorl. Gem and specimen tourmalines are mined chiefly in Brazil and Africa. Placer material suitable for gem use is found in Sri Lanka. In addition to Brazil, tourmaline is mined in Tanzania, Nigeria, Kenya, Madagascar, Mozambique, Namibia, Afghanistan, Pakistan, and Sri Lanka, Malawi, Maine and California.


Hardness: 5.0 - 6.0
Description: Turquoise was among the first gems to be mined, and while many historic sites have been depleted, some are still worked today. These are all small-scale, mostly seasonal operations. They are worked by hand with little or no mechanization. Turquoise is often recovered as a byproduct of copper mining operations, especially in the United States.


Hardness: 7.5
Description: Zircon is a natural stone. It is known as a colorless stone used to imitate diamonds but also comes in: blue, yellow, orange, red, brown and green. It is not to be confused with cubic zirconia, usually a synthetic substance with a completely different chemical composition. Avoid hot water and household chemicals.


Hardness: 8.5 - 9.0
Description: Cubic zirconia (or CZ), is the cubic crystalline form of zirconium dioxide (ZrO2). The synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconium silicate. Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic zirconia has remained the most gemologically and economically important competitor for diamonds since 1976. Its main competition as a synthetic gemstone is the more recently cultivated material, synthetic moissanite.