sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, translucent to opaque, waxy luster, microcrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, translucent to opaque, waxy luster, microcrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity around 2.60 to 2.65.
Formation & geological history
Forms primarily within the cavities of volcanic and metamorphic rocks through the slow deposition of silica-rich groundwater solutions over millions of years.
Uses & applications
Used in ornamental objects, jewelry, decorative carvings, and precision instruments like mortars and pestles.
Geological facts
Agate is a variety of chalcedony and was named by the Greek philosopher Theophrastus after the Achates river in Sicily where stones were found in ancient times.
Field identification & locations
Identified by its distinctive concentric banding, waxy luster, and conchoidal fracture. Commonly found in Brazil, India, Madagascar, and parts of the United States. Ideal for beginner collectors due to its durability and abundance.
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