igneous
Quartz-rich pegmatite, with probable feldspar and mica
Granite/pegmatite assemblage: quartz (SiO₂), feldspar (KAlSi₃O₈–NaAlSi₃O₈–CaAl₂Si₂O₈), and mica
AI-generated identification · may be incorrectCoarse, irregular crystals showing white to translucent quartz, cream/pink feldspar, and dark mica or iron-oxide staining. Quartz is Mohs 7 with glassy luster and no cleavage; feldspar is Mohs 6–6.5 with two cleavages; mica is softer and platy. The image does not support a precise species-level identification.
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Physical properties
Coarse, irregular crystals showing white to translucent quartz, cream/pink feldspar, and dark mica or iron-oxide staining. Quartz is Mohs 7 with glassy luster and no cleavage; feldspar is Mohs 6–6.5 with two cleavages; mica is softer and platy. The image does not support a precise species-level identification.
Formation & geological history
Likely a weathered granitic pegmatite, crystallized slowly from silica-rich magma in a continental crustal setting, commonly hundreds of millions to billions of years old. The reported southern Brazil location is geologically plausible for granitic and pegmatitic material.
Uses & applications
Quartz and feldspar are used in glass, ceramics, abrasives, and construction aggregate; mica is used industrially for insulation and fillers. Attractive crystals may be collected, but these pieces appear mostly rough and low-grade.
Geological facts
Pegmatites can produce exceptionally large crystals and may host tourmaline, beryl, lithium minerals, and rare-earth minerals. The pale blue-gray material could be quartz or altered feldspar, but color alone is insufficient for identification.
Field identification & locations
Look for interlocking coarse crystals, glassy quartz, feldspar cleavage, and flaky mica. A hardness test, streak, acid test, and closer examination of crystal faces would distinguish quartz from feldspar and calcite. Common in Brazilian basement terrains.
