sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, varied colors including gray, white, brown, and blue with banded patterns, waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz 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, varied colors including gray, white, brown, and blue with banded patterns, waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.
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
Used in jewelry, ornaments, carving, mortars and pestles for laboratories, and highly sought after by mineral collectors.
Geological facts
Agate is one of the most popular stones used in art and healing since ancient times, often named after the Achates River in Sicily where they were first found.
Field identification & locations
Can be identified in the field by its distinct concentric banding, waxy luster, and resistance to scratching by a steel knife. Found worldwide, particularly in volcanic rock regions.
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