igneous
Pink granite or granitic pegmatite
Granite; mainly quartz, alkali feldspar, plagioclase, and minor biotite/hornblende
AI-generated identification · may be incorrectCoarse, uneven crystalline texture with salmon-pink feldspar and dark mafic grains; likely Mohs 6–7, vitreous to dull luster, no prominent cleavage as a whole, and specific gravity about 2.6–2.7. The image does not show enough detail for a definitive distinction from pink rhyolite or altered granitic rock.
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Physical properties
Coarse, uneven crystalline texture with salmon-pink feldspar and dark mafic grains; likely Mohs 6–7, vitreous to dull luster, no prominent cleavage as a whole, and specific gravity about 2.6–2.7. The image does not show enough detail for a definitive distinction from pink rhyolite or altered granitic rock.
Formation & geological history
An intrusive felsic igneous rock that crystallized slowly from silica-rich magma, generally millions to billions of years ago. Around 37.8°N, 122.5°W, granitic clasts are plausible in Franciscan Complex-related mélange and local transported beach or fill material.
Uses & applications
Used as dimension stone, aggregate, paving, monuments, and landscaping; attractive pieces may be polished for decorative purposes. This small rough specimen has little commercial value.
Geological facts
The salmon color is usually caused by potassium feldspar, while black patches commonly represent biotite or amphibole. Weathering can make granite appear pinker and more crumbly.
Field identification & locations
Look for interlocking visible crystals, pink feldspar, gray/clear quartz, and black mica or amphibole; a steel nail should not scratch fresh feldspar. Common sources include granitic terrains and transported gravel deposits.
