igneous
Weathered pink granite (probable)
Granite; quartz + feldspar + mica, with iron-oxide staining
AI-generated identification · may be incorrectCoarse, irregular granular texture with pale pink/orange feldspar, gray quartz, and dark mica or alteration minerals; dull to slightly glassy luster. Typical hardness is about 6–7 Mohs, with no consistent cleavage as a rock; the surface appears strongly weathered and iron-stained.
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Physical properties
Coarse, irregular granular texture with pale pink/orange feldspar, gray quartz, and dark mica or alteration minerals; dull to slightly glassy luster. Typical hardness is about 6–7 Mohs, with no consistent cleavage as a rock; the surface appears strongly weathered and iron-stained.
Formation & geological history
Intrusive felsic igneous rock formed when silica-rich magma slowly crystallized deep underground, commonly during Mesozoic or younger continental-magmatic events. The rusty color reflects surface oxidation and weathering.
Uses & applications
Used extensively as dimension stone, countertops, monuments, aggregate, and decorative landscaping rock; this heavily weathered fragment has little commercial or jewelry value.
Geological facts
The pink coloration usually comes from potassium feldspar, while orange-brown patches are commonly limonite/hematite coatings rather than an unusual mineral. The specimen is visually compatible with granitic rocks of the greater San Francisco Bay region.
Field identification & locations
Identify it by interlocking visible grains, pink feldspar, gray quartz, and scattered dark mica; a steel nail should not scratch fresh grains easily. A definitive distinction from rhyolite or altered sandstone requires a fresh break or thin section.
