igneous
Tumbled porphyritic granite
Granite, primarily quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; rounded, dark gray to pink-brown surface with coarse crystalline texture and scattered lighter feldspar grains. Typically vitreous to dull luster, interlocking crystals, and no prominent cleavage as a whole.
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Physical properties
Hardness about 6–7 Mohs; rounded, dark gray to pink-brown surface with coarse crystalline texture and scattered lighter feldspar grains. Typically vitreous to dull luster, interlocking crystals, and no prominent cleavage as a whole.
Formation & geological history
An intrusive igneous rock formed when silica-rich magma cooled slowly underground, allowing large crystals to grow; commonly Precambrian to Phanerozoic in age. The rounded shape indicates natural abrasion or tumbling/polishing.
Uses & applications
Used as dimension stone, countertops, monuments, aggregate, and decorative or lapidary material. A small common tumbled specimen is mainly collectible rather than highly valuable.
Geological facts
The mottled appearance reflects contrasting feldspar, quartz, and dark mafic minerals; pink coloration commonly comes from potassium feldspar. Exact identification is limited because the specimen is small and worn.
Field identification & locations
Look for visible interlocking grains, pink or white feldspar, gray translucent quartz, and black mica or amphibole; it is common in continental crust and sold widely as landscaping or tumbled stone. A hand lens and scratch test help distinguish it from basalt or metamorphic gneiss.
