igneous
Tumbled granite (likely rapakivi or orbicular-textured granite)
Granite, primarily quartz, alkali feldspar, plagioclase, and dark biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; salmon-orange and dark gray-black mottling; granular, crystalline texture with a subdued polished luster. Interlocking crystals show no layering or strong cleavage as a whole, though feldspars have cleavage.
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Physical properties
Hardness about 6–7 Mohs; salmon-orange and dark gray-black mottling; granular, crystalline texture with a subdued polished luster. Interlocking crystals show no layering or strong cleavage as a whole, though feldspars have cleavage.
Formation & geological history
A coarse-grained intrusive igneous rock formed by slow crystallization of silica-rich magma deep in the crust, generally during Precambrian to Phanerozoic events. The rounded shape is from natural stream/beach abrasion or tumbling.
Uses & applications
Used as aggregate, dimension stone, countertops, monuments, landscaping stone, and decorative tumbled material. Common pieces have modest collecting value.
Geological facts
The orange color usually comes from potassium feldspar, while black patches are biotite or amphibole; quartz may appear as gray or translucent grains. This specimen is not confidently identifiable as a specific granite variety from a photograph alone.
Field identification & locations
Look for visible interlocking grains, feldspar-rich pink-orange areas, gray quartz, and black mica/amphibole; it will not fizz with dilute hydrochloric acid. Common worldwide, especially in granitic terrains and glacial or river deposits.
