igneous
Quartz-rich pegmatite fragment
Leucocratic granitic pegmatite, chiefly quartz and feldspar with possible mica
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale gray, white, and rusty-brown surface, with a granular crystalline texture and vitreous to dull luster. Cleavage is weak or absent in quartz but distinct in feldspar; specific gravity approximately 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; pale gray, white, and rusty-brown surface, with a granular crystalline texture and vitreous to dull luster. Cleavage is weak or absent in quartz but distinct in feldspar; specific gravity approximately 2.6–2.7.
Formation & geological history
Formed when water-rich granitic magma cooled slowly in a late-stage vein, allowing coarse crystals to grow; commonly Precambrian to Phanerozoic in age. The brown coloration likely reflects iron-oxide weathering or staining.
Uses & applications
Used locally as decorative stone and a source of quartz, feldspar, mica, and occasionally lithium or gem minerals; this small irregular fragment has minimal commercial value.
Geological facts
The photograph does not show diagnostic crystals clearly enough for a more specific identification; it could also be weathered granite or quartz-bearing vein rock.
Field identification & locations
Common in granitic terrains, pegmatite dikes, and stream gravels worldwide. Look for interlocking quartz and feldspar grains, glassy quartz, and large crystals; a hardness or streak test would improve identification.
