igneous
Tumbled granite (likely granodiorite)
Granite–granodiorite aggregate, chiefly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; rounded and polished, with coarse white feldspar/quartz grains in a dark gray-black matrix. It has a granular crystal structure, vitreous-to-dull luster, and no obvious cleavage as a whole rock; density is typically 2.6–2.8 g/cm³.
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Physical properties
Hardness about 6–7 Mohs; rounded and polished, with coarse white feldspar/quartz grains in a dark gray-black matrix. It has a granular crystal structure, vitreous-to-dull luster, and no obvious cleavage as a whole rock; density is typically 2.6–2.8 g/cm³.
Formation & geological history
A coarse intrusive igneous rock crystallized slowly from magma deep in the crust, generally during Precambrian to Phanerozoic continental pluton formation. The specimen has been mechanically tumbled and polished.
Uses & applications
Used as decorative aggregate, countertops, monuments, building stone, landscaping material, and inexpensive lapidary material. Small tumbled pieces are mainly sold for teaching or collecting.
Geological facts
The contrasting light and dark minerals reflect its felsic-to-intermediate composition; the exact rock name depends on the quartz-to-feldspar ratio. Individual grains crystallized interlocking together, giving granite high durability.
Field identification & locations
Identify it by visible interlocking white/pink feldspar, gray quartz, and black mica or amphibole; it should not fizz with dilute acid and is much harder than calcite. Common sources include granite quarries worldwide, especially North America, Europe, Brazil, and India.
