igneous
Weathered granite pebble
Granitic rock, primarily quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, mottled cream-gray and brown; typically vitreous quartz, dull feldspar, and dark mica/amphibole. Hardness about 6–7 Mohs, granular crystalline texture, poor cleavage as a rock, and specific gravity roughly 2.6–2.8.
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Physical properties
Coarse-grained, mottled cream-gray and brown; typically vitreous quartz, dull feldspar, and dark mica/amphibole. Hardness about 6–7 Mohs, granular crystalline texture, poor cleavage as a rock, and specific gravity roughly 2.6–2.8.
Formation & geological history
Intrusive igneous rock crystallized slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events. The rounded shape and surface staining indicate erosion and weathering.
Uses & applications
Used as crushed aggregate, paving stone, building stone, monuments, and decorative landscaping material; this small weathered specimen has minimal commercial value.
Geological facts
Granite is defined by abundant quartz and alkali feldspar, with visible interlocking crystals. Brown coloration commonly comes from iron oxidation in weathered feldspar or biotite.
Field identification & locations
Identify it by its speckled interlocking grains, lack of layering, and hardness; a steel nail generally fails to scratch fresh quartz grains. Common worldwide, especially in continental shields and mountain belts.
