Thursday, April 23, 2009

What is a Gemstone?

Gemstone is a collective term for all objects used with ornamental stones for personal adornment that possesses beauty, durability, and stability. Beauty, a quality that varies among individuals, can be based on one or any combination of: color or lack of color, luster, transparency, or enhanced optical properties due to cutting and fashioning by the lapidary. Durability is the resistance of the gemstone damage and dependent upon physical properties, such as hardness and tenacity. Tenacity is the resistance to bending and breaking, while hardness measures the resistance to scratch. Diamond cannot be scratched by any other mineral and therefore, it is a gem with high hardness; diamond has low tenacity, in part due to perfect cleavage. Nephrite jade is relatively soft for a gem, easily scratched by dust in the air, but it is composed of fibrous crystals that resist breaking and therefore, it is tough or has high tenacity. Stability refers to the gem's ability to retain color inspite of heat, light, or chemical assaults.

Of the 4,000+ known minerals, 70 possess qualifications for gemstones, but of these, only approximately 20 are commonly encountered (Hurlbut & Kammerling, 1991, p. 3). These minerals include: diamond, corundum (ruby, sapphire, star ruby and sapphire), beryl (emerald, aquamarine, morganite, goshenite, golden or heliodor), chrysoberyl (cat's eye & alexandrite), spinel, topaz, zircon, tourmaline (indicolite, rubellite, schorl, elbaite), garnet group (almandite/almandine, rhodolite, pyrope, grossular/tsavorite, spessartine, uvarovite), quartz: crystalline (rock crystal, amethyst, citrine, cairngorm or smoky, rose, aventurine, tiger's-eye, rutilated), quartz: cryptocrystalline (chrysoprase, carnelian, sard, bloodstone, agate, onyx, jasper, agatized or petrified wood), olivine peridot (chrysolite), jadeite jade, tremolite-actinolite or nephrite jade, spodumene (kunzite, hiddenite), feldspar group (microcline amazonite, labradorite, orthoclase moonstone, oligoclase sunstone), turquoise, lapis-lazuli, and opal.

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