Gem Guide

Alexandrite

Alexandrite

Alexandrite changes from green to red, mauve or brown in incandescent light. Alexandrite has a hardness rating of 8.5. 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.

Amethyst

Amethyst

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. It has a hardness of 7.

Aquamarine

Aquamarine

Aquamarine is light blue, blue-green and dark blue. The highest quality is its transparency. It has a hardness of 7.5 which makes it very tough and protects it to a large extent from scratches. Aquamarine often becomes paler if left out in the sun.

Citrine

Citrine

Citrine is yellow to brown quartz. It varies from pale yellow to rich golden yellow to dark orange. Although citrine may occur naturally, much is produced by heating amethyst under controlled conditions. Darker colors are more highly prized, including medium golden orange ("Rio Grande" citrine) and dark sherry-colored ("Madeira" citrine).

Diamond

Diamond

Diamond is 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. It has a hardness of 10.

Emerald

Emerald

Emerald is medium to dark green beryl. Emerald has a hardness rating of 7.5. The best known sources are Colombia, Zambia. Almost all emeralds contain numerous small inclusions and fractures. Most stones on the market are impregnated with oils, waxes, or other substances to mask the fractures and enhance color.

Garnet

Garnet

Garnet is usually 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. There are various types of garnet with the hardness ranging from 7 - 7.5.

Jade

Jade

There are two types of Jade: Jadeite and Nephrite. Jadeite is rarer comes in many colors: red, yellow, green, lilac, black, orange, white, pink, blue and brown. Jadeite has a hardness of 7. Nephrite Jade is more common. Nephrite Jade comes in various tones of green, mostly with an olive green tone. It has a hardness of 6.5.

Onyx

Onyx

Onyx is a rich-looking, affordable black stone. Onyx, sard, and sardonyx are all varieties of chalcedony. 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. Onyx, sard and sardonyx all have a hardness rating of 7.

Opal

Opal

Opal in large sizes is rare and costly, especially black opal. It is occasionally found as fossilized 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. Opal's scratch hardness is measured at 6.0 to 6.5.

Pearl

Pearl

Pearl is formed in shellfish. The price of pearl varies widely as a result of luster, size, how they were grown, color and type. Natural pearl is the most expensive, followed by cultured pearl, then by fresh water pearl. Pearl is generally white, brown, silver, cream, black or pink depending on the type of shellfish and water. Pearl has a hardness of 3.

Peridot

Peridot

Peridot is a transparent lime or olive green. It has a hardness of 6.5. As with all gems, protect peridot from scratches and sharp blows. Also 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.

Ruby

Ruby

Ruby may be any color of red depending on the chromium and iron content of the stone. Ruby has a hardness rating of 9. Generally, ruby is quite durable, but is subject to chipping and fracture if handled roughly. Ruby is found worldwide, including Myanmar, Afganistan, Pakistan, Vietnam, Thailand, Australia, India, Russia and the USA.

Sapphire

Sapphire

All gem quality corundum that is not red is called sapphire. Unless a color is stated, sapphire is assumed to be blue. Some sapphires will change between blue and violet depending on the light. Sapphire has a hardness of 9. Generally, sapphire is quite durable, but is subject to chipping and fracture if handled roughly.

Tanzanite

Tanzanite

Tanzanite may be blue, purple or slate gray. Tanzanite has a hardness rating of 6.5. 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.

Topaz

Topaz

Topaz comes in many colors such as blue, yellow, pink, brown, green and clear. Orange-red "Imperial" topaz is rare. Topaz has a hardness of 8. As with all gems, protect topaz from scratches and sharp blows.

Tourmaline

Tourmaline

Tourmaline comes in many colors such as blue, yellow, pink, red, black, green and clear, which is why it is still referred to as the 'gemstone of the rainbow'. It has a hardness of 7.5. As with all gems, protect tourmaline from scratches and sharp blows.

Zircon

Zircon

Zircon is a natural stone - not to be confused with Cubic Zirconia which is manmade. It is known as a colorless stone used to imitate diamonds but also comes in: blue, yellow, orange, red, brown and green . It has a hardness of 7.5. Zircon is somewhat soft so avoid scratches and sharp blows. Avoid hot water and household chemicals.