igneous
Quartz-rich pegmatite specimen
Pegmatite, composed mainly of quartz (SiO₂), feldspar, and minor mica/iron oxides
AI-generated identification · may be incorrectCoarse-grained, pale pink to cream, with vitreous quartz and pearly feldspar; quartz hardness 7, feldspar about 6, uneven fracture, and generally low-to-moderate specific gravity (approximately 2.6). Visible cavities and dark inclusions may contain mica or iron-stained minerals.
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Physical properties
Coarse-grained, pale pink to cream, with vitreous quartz and pearly feldspar; quartz hardness 7, feldspar about 6, uneven fracture, and generally low-to-moderate specific gravity (approximately 2.6). Visible cavities and dark inclusions may contain mica or iron-stained minerals.
Formation & geological history
Forms when the final, water-rich melt in a granitic intrusion crystallizes slowly, producing exceptionally large crystals; pegmatites commonly formed during Precambrian to Mesozoic intrusive events. Exact age and locality cannot be determined from the image.
Uses & applications
Used as a source of feldspar, quartz, mica, and occasionally rare-element minerals or gemstones; attractive pieces are sold as cabinet specimens, typically not used as building stone.
Geological facts
The unusually large crystals are the defining feature of pegmatite. Internal cavities, called miarolitic pockets, can host tourmaline, beryl, garnet, or quartz crystals.
Field identification & locations
Identify it by interlocking centimeter-scale crystals, pink/white feldspar, glassy gray-white quartz, and occasional mica flakes. Common in granite-pegmatite districts worldwide, including Brazil, Madagascar, the United States, and Scandinavia.
