igneous
Quartz–feldspar pegmatite with red hematite/stilbite-like crystals
Granitic pegmatite; chiefly quartz (SiO₂), feldspar, mica, and iron-oxide minerals, with possible zeolite-group crystals
AI-generated identification · may be incorrectCoarse crystalline texture; white to gray quartz/feldspar matrix with salmon-red to brown crystal coatings and metallic-to-earthy iron oxides. Quartz hardness 7, feldspar 6–6.5, hematite 5–6; generally vitreous to pearly luster, with feldspar cleavage and no obvious foliation.
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Physical properties
Coarse crystalline texture; white to gray quartz/feldspar matrix with salmon-red to brown crystal coatings and metallic-to-earthy iron oxides. Quartz hardness 7, feldspar 6–6.5, hematite 5–6; generally vitreous to pearly luster, with feldspar cleavage and no obvious foliation.
Formation & geological history
Formed from the final, water-rich fluids of a cooling granitic magma, allowing unusually large crystals to grow in fractures or cavities. Most pegmatites are Precambrian to Mesozoic, but the specimen’s exact age cannot be determined visually.
Uses & applications
Pegmatites are mined for feldspar, quartz, mica, lithium, tantalum, and rare gemstones; attractive pieces are sold as mineral specimens, typically for collecting rather than construction.
Geological facts
The red coloration is likely hematite or iron-stained feldspar; sparkling pale crystals may be quartz, feldspar, or zeolite minerals. Exact identification requires hardness, cleavage, streak, and ideally X-ray or chemical testing.
Field identification & locations
Common in granitic terrains worldwide, including Brazil, Madagascar, the United States, and Scandinavia. Look for very coarse interlocking crystals, glassy quartz, blocky feldspar, and zoned cavities.
