igneous
Tumbled granite, likely orbicular or graphic granite
Granite; chiefly quartz, alkali feldspar, plagioclase, and biotite/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; coarse-grained, cream to gray, with black mafic minerals and a glassy-to-dull polished luster. Interlocking crystalline texture and no consistent cleavage; specific gravity roughly 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; coarse-grained, cream to gray, with black mafic minerals and a glassy-to-dull polished luster. Interlocking crystalline texture and no consistent cleavage; specific gravity roughly 2.6–2.8.
Formation & geological history
A slowly cooled intrusive igneous rock formed from magma deep in the crust, commonly during Precambrian to Phanerozoic continental plutonism. The rounded shape and sheen indicate human tumbling and polishing.
Uses & applications
Used as decorative aggregate, countertops, monuments, building stone, landscaping material, and inexpensive polished specimens. It has modest collector value unless it displays unusual orbicular patterns or notable provenance.
Geological facts
The black areas are probably biotite mica and/or amphibole, while the pale grains are feldspar and quartz. Exact identification may require a hand lens, streak test, and thin-section or X-ray analysis.
Field identification & locations
Identify by its visible interlocking grains, abundant pale feldspar/quartz, black minerals, and lack of layering or foliation; unlike marble, it is not composed mainly of calcite and will not fizz strongly in dilute acid. Common worldwide, especially in India, Brazil, Scandinavia, and North America.
