sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline quartz crystal structure, conchoidal fracture, variable colors including brown, grey, white, and orange, specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline quartz crystal structure, conchoidal fracture, variable colors including brown, grey, white, and orange, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed mainly in cavities of eruptive rocks or ancient lavas through the deposition of silica from groundwater solutions, typically over millions of years.
Uses & applications
Used primarily in jewelry, ornamental carvings, polished specimens, and industrial bearings or mortars due to its hardness.
Geological facts
Agates often display distinct concentric banding patterns formed by the rhythmic deposition of silica layers within gas cavities in volcanic rocks.
Field identification & locations
Easily identified by its characteristic waxy luster, hardness that scratches glass, and often banded appearance. Found worldwide, particularly in regions with volcanic history.
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