metamorphic
Polished mica-rich metamorphic sphere
Likely mica schist or garnet-mica schist; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectGray-green to silvery matrix with reflective platy mica, irregular dark inclusions, and a polished luster. Mica has perfect basal cleavage and Mohs hardness about 2–3; associated quartz/feldspar is about 6–7, with overall specific gravity commonly 2.7–3.2.
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Physical properties
Gray-green to silvery matrix with reflective platy mica, irregular dark inclusions, and a polished luster. Mica has perfect basal cleavage and Mohs hardness about 2–3; associated quartz/feldspar is about 6–7, with overall specific gravity commonly 2.7–3.2.
Formation & geological history
Formed when clay-rich sedimentary rock underwent regional metamorphism, recrystallizing into aligned mica with quartz and feldspar; garnet or opaque minerals may form during higher-grade metamorphism. Commonly Paleozoic or Precambrian, depending on source terrain.
Uses & applications
Usually sold as a decorative, polished stone sphere or collector specimen; schist is occasionally used as facing stone, aggregate, or low-volume dimension stone, but mica-rich varieties are generally unsuitable for heavy construction.
Geological facts
The bright flashes come from mica cleavage surfaces rather than metallic metal. A sphere may obscure the original foliation, so visual identification is provisional.
Field identification & locations
Look for visible flaky mica, planar foliation, sparkly cleavage, and uneven hardness; a streak, hardness, and thin-section test would confirm it. Common sources include Brazil, India, Madagascar, and other metamorphic belts.
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