igneous
Tumbled yellow granite or granitic gneiss
Granite, chiefly quartz, feldspar, and biotite/amphibole
AI-generated identification · may be incorrectTypically Mohs 6–7; yellow to tan with black mineral flecks, granular texture, and a vitreous-to-dull luster. Interlocking crystals and lack of cleavage are characteristic; the rounded shape is from tumbling or natural abrasion.
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Physical properties
Typically Mohs 6–7; yellow to tan with black mineral flecks, granular texture, and a vitreous-to-dull luster. Interlocking crystals and lack of cleavage are characteristic; the rounded shape is from tumbling or natural abrasion.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in Earth’s crust, generally during Precambrian to Phanerozoic events; yellow coloration commonly results from weathered or iron-stained feldspar. The exact rock type cannot be confirmed without a fresh surface or testing.
Uses & applications
Used as aggregate, building stone, countertops, monuments, landscaping material, and inexpensive tumbled decorative stone.
Geological facts
The black grains are likely biotite mica or amphibole, while the yellow background is feldspar-rich. A glassy quartz grain may be visible among the feldspar crystals.
Field identification & locations
Common in continental crust and glacial or river gravels worldwide. Identify it by its speckled, coarse-grained texture; a streak test, hardness test, and close inspection of a broken surface can distinguish it from jasper or dyed stone.
