igneous
Quartz-rich pegmatitic rock (likely quartz–feldspar–mica specimen)
Granitic pegmatite; mainly quartz (SiO₂), feldspar, and dark mica/amphibole
AI-generated identification · may be incorrectHardness about 6–7; white to gray, with vitreous quartz and pearly-to-submetallic dark mica or amphibole. Coarse interlocking crystals, irregular fracture, and feldspar cleavage are visible; exact density and minerals require testing.
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Physical properties
Hardness about 6–7; white to gray, with vitreous quartz and pearly-to-submetallic dark mica or amphibole. Coarse interlocking crystals, irregular fracture, and feldspar cleavage are visible; exact density and minerals require testing.
Formation & geological history
Likely crystallized slowly from volatile-rich granitic magma in a pegmatite vein, commonly during Precambrian to younger continental crust formation. The rounded shape appears naturally weathered or tumbled.
Uses & applications
Used mainly as a collecting specimen; pegmatites can supply quartz, feldspar, mica, lithium, and rare-element minerals, while related granite is used for construction and countertops.
Geological facts
The dark material may be biotite mica, tourmaline, or hornblende; a hand lens and streak, hardness, and cleavage tests can distinguish them.
Field identification & locations
Look for very coarse crystals, glassy quartz, blocky feldspar, and platy black mica; common in granitic terrains worldwide, including Brazil, the United States, Madagascar, and Scandinavia. A definitive identification needs a fresh surface or analytical testing.
