igneous
Weathered quartz-rich pegmatite, likely feldspar/quartz
Granitic pegmatite; chiefly microcline or plagioclase feldspar (KAlSi₃O₈–NaAlSi₃O₈) with quartz (SiO₂), possibly mica
AI-generated identification · may be incorrectHardness roughly 6–7 (feldspar to quartz); white to cream with rusty iron-oxide staining, pearly-to-glassy luster, coarse interlocking crystals, and prominent feldspar cleavage. The specimen appears fractured and weathered rather than gem quality.
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Physical properties
Hardness roughly 6–7 (feldspar to quartz); white to cream with rusty iron-oxide staining, pearly-to-glassy luster, coarse interlocking crystals, and prominent feldspar cleavage. The specimen appears fractured and weathered rather than gem quality.
Formation & geological history
Pegmatites crystallize slowly from the final, water-rich fluids of granitic magma, producing exceptionally coarse crystals. Most formed during ancient Precambrian–Phanerozoic intrusive events, commonly alongside granite.
Uses & applications
Used as a source of feldspar and quartz for ceramics, glass, and industrial materials; attractive pieces are collected, though this fragment has little jewelry use.
Geological facts
The blocky, planar cleavage and pale color favor feldspar, while any translucent glassy zones may be quartz. Iron staining commonly develops from weathering of mica or sulfide-bearing fractures.
Field identification & locations
Common in granitic and metamorphic terrains worldwide, including Maine, California, Brazil, Madagascar, and Scandinavia. Check for hardness, cleavage, and a white streak; a glass-scratching test can distinguish quartz from softer feldspar.
