igneous
Pegmatitic granite
Granitic pegmatite; chiefly quartz (SiO₂), feldspars, and mica
AI-generated identification · may be incorrectCoarse-grained, interlocking crystals with white to pink feldspar, translucent gray quartz, and dark mica; vitreous quartz luster and Mohs hardness about 6–7. Crystals are irregular to blocky, with feldspar cleavage and no consistent overall cleavage.
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Physical properties
Coarse-grained, interlocking crystals with white to pink feldspar, translucent gray quartz, and dark mica; vitreous quartz luster and Mohs hardness about 6–7. Crystals are irregular to blocky, with feldspar cleavage and no consistent overall cleavage.
Formation & geological history
Forms when silica-rich magma cools slowly, commonly in the late-stage margins of granite intrusions; individual pegmatite bodies may be Precambrian to Cenozoic. The specimen appears weathered and partly altered, with iron staining and mica-rich patches.
Uses & applications
Used mainly as a collector specimen; feldspar and quartz pegmatites may provide ceramic feldspar, silica, mica, lithium, or gemstones. Attractive polished pieces can be used decoratively.
Geological facts
Its unusually large crystals reflect volatile-rich residual magma and slow underground cooling. Pink coloration commonly comes from potassium feldspar, while silvery or dark flakes are mica.
Field identification & locations
Identify by its very coarse texture, visible quartz, pink/white feldspar, and flaky mica; distinguish it from ordinary granite by markedly larger crystals. Common worldwide, especially in Brazil, Madagascar, the United States, and Scandinavia.
