igneous
Pegmatitic granite (quartz–feldspar–mica rock)
Granitic pegmatite; primarily quartz (SiO₂), alkali/plagioclase feldspar, and minor mica, with iron-oxide staining
AI-generated identification · may be incorrectCoarse, irregular interlocking crystals; pale cream to gray with brown-red weathering. Quartz hardness 7 and feldspar about 6, vitreous to earthy luster, no strong overall cleavage, and typical bulk specific gravity near 2.6–2.7.
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Physical properties
Coarse, irregular interlocking crystals; pale cream to gray with brown-red weathering. Quartz hardness 7 and feldspar about 6, vitreous to earthy luster, no strong overall cleavage, and typical bulk specific gravity near 2.6–2.7.
Formation & geological history
Slow crystallization of silica-rich magma produced large crystals, commonly in dikes or veins cutting older continental crust; the specimen is likely Paleozoic to Precambrian in age, depending on locality.
Uses & applications
Used as decorative stone, aggregate, and occasionally a source of feldspar, quartz, mica, or rare pegmatite minerals; this piece has limited jewelry value.
Geological facts
The reddish-brown patches are probably hematite/limonite staining or altered mica rather than a separate gemstone. The unusually coarse texture is the key pegmatitic feature.
Field identification & locations
Look for visibly large quartz and feldspar grains, glassy gray quartz, blocky feldspar cleavage, and scattered mica flakes; common in Precambrian shields and granite regions worldwide.
