igneous
Quartz-rich pegmatite with mica
Granitic pegmatite; mainly quartz (SiO₂), feldspar, and muscovite/biotite mica, with possible sulfide or iron-oxide staining
AI-generated identification · may be incorrectCoarse, irregular interlocking crystals; pale gray-white quartz, cream feldspar, and reflective gold-brown mica. Hardness: quartz 7, feldspar 6, mica 2–3; vitreous to pearly luster, no consistent cleavage in quartz but prominent cleavage in mica.
- Hardness
- quartz 7, feldspar 6, mica 2–3
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Physical properties
Coarse, irregular interlocking crystals; pale gray-white quartz, cream feldspar, and reflective gold-brown mica. Hardness: quartz 7, feldspar 6, mica 2–3; vitreous to pearly luster, no consistent cleavage in quartz but prominent cleavage in mica.
Formation & geological history
Formed when water-rich granitic magma cooled slowly in a late-stage vein or pocket, allowing exceptionally large crystals to grow. Most pegmatites are Precambrian to Mesozoic, depending on locality.
Uses & applications
Used as a source of quartz, feldspar, mica, lithium, and rare gemstones; attractive pieces are collected, though this specimen appears primarily cabinet-grade rather than jewelry-grade.
Geological facts
The flaky golden material is likely mica, while dark patches may be biotite, tourmaline, sulfides, or weathering products; a photo cannot distinguish these reliably.
Field identification & locations
Common in granite terrains and mineral-collecting districts. Check for glassy quartz, blocky feldspar, and sheets that peel or sparkle; streak, hardness, and acid testing can help identify accessory minerals.
