igneous
Pink granite or rhyolite cobble
Felsic igneous rock, likely weathered granite; mainly quartz, feldspar, and minor biotite/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; salmon-pink, fine- to medium-grained appearance with dark mafic specks, dull to slightly sugary luster, and no obvious cleavage as a whole rock. The rounded shape indicates prolonged water or glacial abrasion, while surface pits may reflect weathered inclusions.
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Physical properties
Hardness about 6–7 Mohs; salmon-pink, fine- to medium-grained appearance with dark mafic specks, dull to slightly sugary luster, and no obvious cleavage as a whole rock. The rounded shape indicates prolonged water or glacial abrasion, while surface pits may reflect weathered inclusions.
Formation & geological history
Formed when silica-rich magma cooled underground as granite, or more rapidly near the surface as rhyolite; exact age cannot be determined from the photograph. Commonly derived from Precambrian to Mesozoic continental crust and later transported as a cobble.
Uses & applications
Used as decorative landscaping stone, aggregate, monuments, countertops, and building stone; attractive pieces may be polished, but ordinary cobbles have minimal commercial value.
Geological facts
The pink color generally comes from potassium feldspar, while dark grains are biotite or amphibole. A coarse granular texture would favor granite; a uniformly fine texture would favor rhyolite.
Field identification & locations
Look for visible interlocking quartz and feldspar grains, glassy quartz, and pink potassium feldspar; a hand lens and hardness test help distinguish it from pink sandstone or artificial material. Common in granite-rich mountain regions, glacial deposits, streambeds, and beaches.
