igneous
Weathered granite or granitic gneiss pebble
Granite; mainly quartz, feldspar, and mica
AI-generated identification · may be incorrectHardness about 6–7 Mohs; light gray to tan, granular, and dull to slightly sparkly. The rounded shape indicates water or abrasion weathering; visible grains suggest interlocking quartz and feldspar, though the image is insufficient to confirm gneissic banding.
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Physical properties
Hardness about 6–7 Mohs; light gray to tan, granular, and dull to slightly sparkly. The rounded shape indicates water or abrasion weathering; visible grains suggest interlocking quartz and feldspar, though the image is insufficient to confirm gneissic banding.
Formation & geological history
Formed when silica-rich magma slowly crystallized deep underground, typically during Precambrian to Phanerozoic continental crust formation; later exposed and rounded by erosion. Exact age and provenance cannot be determined visually.
Uses & applications
Commonly used as crushed aggregate, building stone, countertops, monuments, and landscaping rock; this small specimen has little commercial value.
Geological facts
Granite commonly contains pink or white feldspar, glassy gray quartz, and black mica or amphibole. Its resistance to weathering allows it to persist as rounded stream and beach cobbles.
Field identification & locations
Look for distinct interlocking grains, quartz’s glassy appearance, feldspar cleavage, and no reaction to dilute hydrochloric acid; a streak or hardness test can help. Common worldwide, especially in continental shield and mountain regions.
