igneous
Tumbled granite (likely granite or granitic gneiss)
Granite; chiefly quartz (SiO₂), feldspar, and mica, with possible alteration minerals
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pink, white, gray, and dark green-black grains; granular texture and mostly vitreous to dull luster. Interlocking crystals are visible, with no obvious cleavage on the polished surface; typical specific gravity is 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; pink, white, gray, and dark green-black grains; granular texture and mostly vitreous to dull luster. Interlocking crystals are visible, with no obvious cleavage on the polished surface; typical specific gravity is 2.6–2.8.
Formation & geological history
A coarse-grained intrusive igneous rock formed by slow cooling of silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events. The rounded shape indicates tumbling and polishing rather than natural weathering alone.
Uses & applications
Used as a decorative stone, aggregate, countertops, monuments, landscaping material, and inexpensive polished-stone specimens.
Geological facts
The pink areas are commonly potassium feldspar, pale areas are quartz or plagioclase, and dark grains are biotite, amphibole, or alteration products.
Field identification & locations
Identify it by its speckled, interlocking crystals and lack of layering or vesicles; a streak test is unhelpful, while a steel scratch test may be resisted. Common worldwide, especially in continental shields and mountain belts.
