igneous
Quartz-rich feldspathic pebble, possibly granite or granitic gneiss
Quartz–feldspar aggregate, likely granite; dark inclusion may be biotite, hornblende, or iron-oxide staining
AI-generated identification · may be incorrectHardness about 6–7 Mohs; rounded tan, cream, and gray surface with a granular texture and mostly dull to vitreous luster. Visible interlocking grains suggest quartz and feldspar, with a dark mafic mineral inclusion; cleavage is not obvious in the weathered pebble.
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Physical properties
Hardness about 6–7 Mohs; rounded tan, cream, and gray surface with a granular texture and mostly dull to vitreous luster. Visible interlocking grains suggest quartz and feldspar, with a dark mafic mineral inclusion; cleavage is not obvious in the weathered pebble.
Formation & geological history
Likely eroded from an ancient felsic plutonic or metamorphic body, crystallized slowly underground over hundreds of millions to billions of years, then rounded by stream or shoreline transport.
Uses & applications
Common granite is used for aggregate, building stone, countertops, monuments, and landscaping; attractive polished pieces may be used as specimens or cabochon material.
Geological facts
The tan color commonly results from weathering or iron staining of feldspar. A dark mineral-rich patch is typical of mafic inclusions or biotite clusters in granitic rocks.
Field identification & locations
Look for visible quartz, feldspar, and dark mica/hornblende grains; a steel nail should not easily scratch fresh quartz-rich areas. Exact identification requires a fresh broken surface or thin section; common in stream gravels and glacial deposits worldwide.
