igneous
Quartz-rich pegmatite specimen
Quartz (SiO₂) with probable feldspar and mica inclusions
AI-generated identification · may be incorrectCoarse, interlocking crystals; white to translucent quartz with cream/pink feldspar and dark mica or iron-oxide staining. Quartz is Mohs 7, vitreous, hexagonal; feldspar is Mohs 6–6.5 with two cleavages. Specific gravity is roughly 2.6–2.7.
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Physical properties
Coarse, interlocking crystals; white to translucent quartz with cream/pink feldspar and dark mica or iron-oxide staining. Quartz is Mohs 7, vitreous, hexagonal; feldspar is Mohs 6–6.5 with two cleavages. Specific gravity is roughly 2.6–2.7.
Formation & geological history
Likely a granitic pegmatite formed when silica-rich magma cooled slowly in a late-stage vein, allowing very large crystals to grow. Pegmatites are generally Precambrian to Phanerozoic, depending on locality.
Uses & applications
Used as a collector specimen; quartz and feldspar from pegmatites are important in glass, ceramics, electronics, and construction aggregate. Attractive crystal-rich pieces may be decorative.
Geological facts
The blocky cream crystals are probably feldspar, while translucent gray-white areas are quartz; rusty colors commonly reflect oxidized iron. Exact identification requires a fresh surface, hardness testing, and possibly acid or thin-section analysis.
Field identification & locations
Common in granitic terrains worldwide, especially Brazil, Madagascar, the United States, and Scandinavia. Look for exceptionally coarse crystals, glassy quartz, feldspar cleavage, and mica flakes; avoid confusing it with ordinary granite.
