gem, ornamental mineral or organic substance: Precious and Semiprecious Gemstones

The precious stones are diamond; some forms of corundum (ruby, sapphire, Oriental emerald, Oriental topaz, and Oriental amethyst); and emerald. The chief semiprecious stones are aquamarine, amethyst, topaz, garnet, tourmaline, spinel, peridot (see olivine), zircon (see zirconium), chrysoberyl, quartz, opal, turquoise, moonstone, and jade. The organic gems are pearl, amber, coral, and jet; of these, pearl is usually counted as a precious stone.

Sections in this article:

• Introduction
• Counterfeit Gemstones
• Precious and Semiprecious Gemstones
• Other Gemstones
• Diamond Cutting
• Gem Cutting
• Properties of Gems
• Bibliography

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