igneous
Quartz-rich pegmatite specimen
Pegmatite, composed mainly of quartz (SiO₂), with probable feldspar and mica
AI-generated identification · may be incorrectCoarse-grained, irregular interlocking crystals; white to gray quartz with pearly white feldspar and possible dark mica. Quartz hardness 7, vitreous luster, no cleavage; feldspar hardness 6–6.5 with two cleavages. Specific gravity commonly 2.6–2.7.
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Physical properties
Coarse-grained, irregular interlocking crystals; white to gray quartz with pearly white feldspar and possible dark mica. Quartz hardness 7, vitreous luster, no cleavage; feldspar hardness 6–6.5 with two cleavages. Specific gravity commonly 2.6–2.7.
Formation & geological history
Formed when water-rich granitic magma crystallized slowly in a late-stage dike or vein, allowing exceptionally large crystals to grow. Typically Precambrian to Phanerozoic, depending on its host intrusion.
Uses & applications
Used as a source of quartz and feldspar for glass, ceramics, and industrial materials; attractive pieces are collected as cabinet specimens. This irregular fragment has modest ornamental value.
Geological facts
Pegmatites can host spectacular crystals of tourmaline, beryl, spodumene, and rare-element minerals. The image most strongly suggests a weathered quartz–feldspar aggregate, but exact identification requires testing.
Field identification & locations
Common in and around granite bodies worldwide, including Brazil, Madagascar, the United States, and Scandinavia. Look for very coarse crystals, glassy quartz, blocky feldspar, and mica; a streak, hardness, and acid test can refine identification.
