sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, variable colors due to impurities, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, variable colors due to impurities, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65
Formation & geological history
Forms primarily within the cavities of volcanic or metamorphic rocks through the deposition of silica from groundwater solutions, often in concentric bands
Uses & applications
Used in making jewelry, ornamental items, mortars and pestles for laboratory use, and appreciated by mineral collectors
Geological facts
Agate is one of the most popular materials used in hardstone carving and was prized as a talisman in ancient civilizations for its supposed healing and protective properties
Field identification & locations
Easily identified by its waxy luster, conchoidal fracture, and often banded appearance. Found worldwide in river gravels and volcanic regions
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