Agate, along with carnelian, chrysoprase, jasper, and flint, is a variety of chalcedony, a type of quartz made up of tiny crystalline fibers. Agate has a striking color banding due to slight differences in the compositions and grain sizes of the crystalline fibers.

Class: semiprecious
Origin of Name: from the Latin achates, the former name of Sicily's river Drillo, along which agate was found in ancient times
Color: green, yellow, red, reddish-brown, white, bluish-white
Chemical Composition: silica
Crystal System: trigonal (microcrystalline)
Hardness: 6.5
Specific Gravity: 2.57-2.64
Geographic Origins: worldwide but chiefly Brazil and Uruguay


Photo: ©International Colored Gemstone Association/Bart Curren

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