Agate - By: Fashion Jewelry, 2008-06-06

Agate is a variety of chalcedony which comprises cryptocrystalline quartz gemstones composed of layers of quartz, sometimes of different colors. Agate is usually found as rounded nodules or veins. The layers of quartz are often concentric. The composition of agate varies greatly, but silica is always predominant, usually with alumina and oxide of iron.

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