sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, translucent to opaque, conchoidal fracture, specific gravity of 2.58 to 2.64, displays multicolored bands or patterns.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, translucent to opaque, conchoidal fracture, specific gravity of 2.58 to 2.64, displays multicolored bands or patterns.
Formation & geological history
Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions over millions of years.
Uses & applications
Widely used in jewelry, ornamental carvings, polished specimens, mortars and pestles for laboratory use, and as a popular collector's mineral.
Geological facts
Agate was named by Theophrastus, a Greek philosopher and naturalist, after the Achates river in Sicily where stones were found in antiquity.
Field identification & locations
Found worldwide in volcanic regions, particularly Brazil, Uruguay, India, and various parts of the USA. Identified by its banded patterns and hardness.
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