Achroite colorless variety of tourmaline. Hardness of 7 - 7,5
Agate translucent to opaque, semi-precious variety of chalcedony (quartz)
Alexandrite rare mineral/gem (type of chrysoberyl) that appears to be different colors when viewed in artificial or natural light.
Almandine reddish variety of garnet. Hardness of 6,5 - 7,5
Amazonite semi-precious stone (blue to bluish-green), variety of feldspar-family.
Amethyst most popular quartz-variety (deep purple to pale lavender)
Ametrine (partially purple/lavender and orange/yellow quartz-variety (amethyst and citrine).
Apatite semi-precious mineral that occurs in many different colors, hardness of 5
Aquamarine very popular (blue) variety of the beryl-family
Aventurine semi-precious, translucent variety of the quartz-family
Beryl gemstone-group, including emerald, aquamarine, morganite, heliodor, bixbite and goshenite.
Birthstone worldwide assigned stones to the months of the year
Brilliant Cut faceted round cut (32 facets above the girdle, 24 facets below)
Cabochon rounded cut (usually with a domed surface) - no facets
Carat standard measure of gemstone-weight. One carat weights 0,2 gram.
Chalcedony mostly milky or translucent semi-precious stones of the quartz-family, including cornelian, chrysoprase, onyx, jasper
Charoite semi-precious,opaque mineral (purplish), only found in Russia
Chrome-Diopside intense green-colored gemstone, hardness of 5 - 6
Chrysoberyl yellowish to green and brown colored gemstone, hardness of 8,5
Chrysocolla opaque, blue to bluish-green semi-precious mineral, hardness of 2 - 4
Chrysoprase most valued, semi-precious quarzt-variety (green)
Citrine pale yellow to orange quarzt-variety. Hardness of 7
Clarity clearness of gemstones
Cornelian semi-precious, tranlucent variety (reddish) of chalcedony-quartz.
Corundum second hardest mineral on earth (hardness of 9). Depending on the color there are two precious varieties: ruby and sapphire
Crown upper part of a faceted gemstone
Danburite usually colorless gemstone, hardness of 7 - 7,5
Demantoid most expansive and rare variety (green) of garnet, hardness of 6,5 - 7,5
Diamond precious gemstone, made of compressed carbon, hardness 10
Doublet gemstone made of two layers - the upper part is usually the precious stone, the bottom-part is semi-precious.
Emerald precious green gemstone, variety of beryl. Hardness of 7,5 - 8
Enhanced gemstones will be treated to improve the color or clarity. Heat-treatment is very common, all other methods (irradiation, coating, oiling, diffussion etc) have to be declared.
Facetting cutting and polishing of the gemstone surface
Fancy Diamond colored diamonds (all colors, except white), hardness of 10
Fancy cut Unusual cut (faceted or cabochon)
Feldspar most common (semi-precious) mineral-family on earth, hardness of 4 - 6,5
Fire Opal transparent opals (yellow, orange, red), mostly milky. Hardness of 5,5 - 6,5
Fluorite semi-precious mineral that occurs in many colors, hardness of 4
Garnet group of minerals/gems that occurs in a wide range of colors. Hardness of 6,5 - 7,5
Gemstone rare, valuable and attractive mineral (usually faceted)
GIA Gemological Institute of America
Goshenite Colorless variety of beryl. Hardness of 7,5 - 8
Grossular Variety of garnet, hardness of 6,5 - 7,5
GLA Gem Lab Austria (Vienna)
Hematite opaque, silver to black colored semi-precious stone, hardness of 6,5
Hessonite Variety of garnet, hardness of 6,5 - 7,5
Hiddenite yellow to green variety of the mineral spodumene, hardness of 6,5 - 7
IGI International Gemological Institute
Imperial Topaz most valuable topaz-variety (golden-orange-pinkish), hardness of 8
Indicolite blue variety of tourmaline. Hardness
Iolite blue mineral/gem with strong pleochroism, hardness of 7 - 7,5
Irradiation radiation-treatment to enhance colors of gemstones
Jade semi-precious stone, often set as cabochon in best (green & translucent) quality. Hardness of 6 - 7
Jasper semi-precious stone, variety of quartz. Hardness of 6,5 - 7
Kunzite pink variety of the mineral spodumene, hardness of 6,5 - 7
Kyanite blue gemstone, mostly with color-zoning. Hardness 4,5 - 6 - very difficult to cut!
Labradorite variety of the semi-precious feldspar-group (plagioclase). Hardness 6 - 6,5
opaque, blue semi-precious stone. Hardness of 5,5
Mandarin-Garnet orange variety of garnet (spessartite-group), hardness of 7 - 7,5
Malachite opaque, semi-precious stone (green-banded), Hardness of 4
Mohs-scale This scale shows a chart of relative hardness of various minerals (1 = softest, 10 = hardest).

Hardness Example

calcite, a penny
most glass
feldspar (spectrolite)
quartz (amethyst, citrine, agate)
steel file
beryl (emerald, aquamarine)
corundum (ruby, sapphire)
Morganite pink variety of beryl. Hardness of 7,5 - 8
Moonstone semi-transparent to translucent variety of feldpar. It occurs in different colors (white, pale yellow, grey, orange, brown and reddish) Hardness of 6 - 6,5
Obsidian semi-precious stone (transparent - opaque), hardness of 5
Onyx semi-precious variety of chalcedony (quartz). Hardness of 6,5 - 7
Opal very popular gemstone (3 major types), containing water (!). Hardness of 5,5 - 6,5
Opaque light is not possible to pass through (no brilliance)
Padparadscha beautiful, pinkish-orange sapphire-color, rare found in Sri Lanka
Peridot green gemstone of vivid color. Hardness of 6,5 - 7
Pleochroism the property of having more than only one color, especially when the gemstone is viewed from different angles
Precious Stone rare and valuable gemstone
Pyrope reddish variety of garnet. Hardness of 6,5 - 7,5
Pyrite opaque, semi-precious stone (metallic). Hardness of 6 - 6,5
Quartz the second common mineral on earth, including amethyst, ametrine, citrine, rose quarz, aventurine, rock crystal, chalcedony, chrysoprase and many others
Rhodolite pinkish-red variety of garnet (combination of pyrope and almandine). Hardness of 7 - 7,5
Rock Crystal colorless variety of quartz, also called white quarz. Hardness of 7
Rose Quartz pale pink to pink variety of quartz (mostly silky). Hardness of 7
Rubellite reddish variety of tourmaline. Hardness of 7 - 7,5
Ruby reddish variety of corundum. Actually one of the most expansive gemstones. Hardness of 9
Rutilated Quartz Variety of quartz, containing fine needles of rutile-crystals.
Sapphire all color-varieties of corundum, except red. One of the most popular and expansive gemstones. Hardness of 9.
Sillimanite rare gem/mineral, ranging in color from colorless, yellow, greyish, greenish to brown. Hardness of 6,5 - 7,5
Smoky Quartz brownish (smoky) variety of quarz. Hardness of 7
Sodalite blue and opaque, semi-precious stone, Hardness of 5,5 - 6
Spessartite reddish or orange variety of garnet. Hardness of 7 - 7,5
Spinel attractive gemstone which ranges in color from yellow to black. Hardness of 8
Sunstone reddish-orange (metallic) variety of feldspar (oligoclase). Hardness of 6
Tanzanite exclusive bluish-purple gemstone from Tanzania in East-Africa. Hardness of 6,5 - 7
Tsavorite exclusive green variety of garnet (grossular-group). Hardness of 6,5 - 7,5
Tiger´s Eye yellowish-brown, opaque variety of the quarz-family. Hardness of 7
Topaz popular gemstone, ranges in color from colorless to yellow, to orange to pink and brown. Hardness of 8
Tourmaline the only gemstone which occurs in all colours. Hardness of 7 - 7,5
Translucent light is able to pass through, but it is scattered
Transparent light is able to pass through without any diffusing
Turquoise semi-precious, opaque stone with typical color. Hardness of 6
Unakit opaque, semi-precious stone (containing granite, epidote and feldspar). Hardness of 6,5 - 7
Zircon natural gemstone, occuring in many different colours. Hardness of 6,5 - 7,5

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