mineral
Spherulitic Agate / Moss Agate
Chalcedony (SiO2) with mineral inclusions
Hardness: 6.5-7 on the Mohs scale. Translucent grayish-purple chalcedony base containing brown and yellow orbicular, spherulitic, or moss-like inclusions. Vitreous to waxy luster. Conchoidal fracture.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 on the Mohs scale. Translucent grayish-purple chalcedony base containing brown and yellow orbicular, spherulitic, or moss-like inclusions. Vitreous to waxy luster. Conchoidal fracture.
Formation & geological history
Formed via low-temperature hydrothermal deposition of silica-rich solutions filling cavities in volcanic rocks (such as basalt or rhyolite). The inclusions consist of iron oxides or chlorite that precipitated in orbicular structures before or during chalcedony growth.
Uses & applications
Used primarily as a lapidary material, cut into cabochons, polished decorative pieces, or collected by rockhounds.
Geological facts
The tiny circular and ring-like inclusions are known as spherulites or orbicules, created by radial mineral growth during silica gel precipitation inside volcanic gas pockets.
Field identification & locations
Identified by translucent chalcedony body containing distinct ringed or mossy orbicular mineral inclusions and smooth conchoidal fracture. Commonly found in volcanic agate deposits worldwide, including Brazil, Madagascar, and the western United States.
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