igneous
Granite (likely biotite granite or granodiorite)
Coarse-grained granitoid composed mainly of quartz, feldspar, and dark biotite/amphibole
AI-generated identification · may be incorrectTypically Mohs 6–7; mottled white, gray, black, and pale green with a granular texture and vitreous-to-dull luster. Interlocking crystals show no regular cleavage as a whole, though feldspar and mica cleave individually; the specimen appears naturally weathered or roughly shaped.
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Physical properties
Typically Mohs 6–7; mottled white, gray, black, and pale green with a granular texture and vitreous-to-dull luster. Interlocking crystals show no regular cleavage as a whole, though feldspar and mica cleave individually; the specimen appears naturally weathered or roughly shaped.
Formation & geological history
Formed when silica-rich magma slowly crystallized deep in Earth’s crust, commonly during Precambrian to Phanerozoic mountain-building events. Its greenish tint may reflect altered feldspar, epidote, or other secondary minerals.
Uses & applications
Widely used as dimension stone, countertops, monuments, aggregate, and decorative rock; attractive hand specimens are collected but usually have modest value.
Geological facts
Granite is defined by abundant quartz and alkali feldspar, whereas granodiorite contains more plagioclase. The visible coarse crystals indicate slow underground cooling rather than volcanic eruption.
Field identification & locations
Identify it by its speckled, interlocking crystals, inability to scratch with a steel knife, and quartz grains that may scratch glass. Common worldwide, especially in continental shields and mountain belts.
