igneous
Granite (likely weathered biotite granite)
Coarse-grained felsic plutonic rock; quartz + alkali feldspar/plagioclase + biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pink, white, gray, and black granular crystals with vitreous quartz and dull feldspar. Massive, nonfoliated texture, with no prominent cleavage as a whole; specific gravity roughly 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; pink, white, gray, and black granular crystals with vitreous quartz and dull feldspar. Massive, nonfoliated texture, with no prominent cleavage as a whole; specific gravity roughly 2.6–2.7.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, commonly during Precambrian to Mesozoic mountain-building events; the exact age requires laboratory analysis.
Uses & applications
Widely used as dimension stone, countertops, monuments, aggregate, and paving; attractive polished pieces are collected but usually have modest value.
Geological facts
The mottled appearance reflects interlocking quartz, feldspar, and dark mafic minerals; greenish patches may represent epidote or chlorite from alteration.
Field identification & locations
Identify by its visible interlocking crystals, pink/white feldspar, gray quartz, and scattered black mica or amphibole; it is common in continental shields and mountain belts worldwide. Estimated value: $1–$10 as a common hand specimen, or $20–$75 if unusually attractive and polished.
