igneous
Coarse-grained granite pegmatite
Granitic pegmatite; mainly quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectHardness about 6–7 overall; pale gray to pink with glassy quartz, blocky feldspar, and shiny mica. Coarse interlocking crystals, irregular fracture, and low-to-moderate specific gravity (~2.6).
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Physical properties
Hardness about 6–7 overall; pale gray to pink with glassy quartz, blocky feldspar, and shiny mica. Coarse interlocking crystals, irregular fracture, and low-to-moderate specific gravity (~2.6).
Formation & geological history
An intrusive igneous rock formed when water-rich granitic magma cooled slowly, allowing unusually large crystals to grow; commonly Precambrian to younger in age. The specimen appears weathered and may contain minor iron staining.
Uses & applications
Used locally as decorative stone, aggregate, and a source of feldspar, quartz, mica, and occasional lithium or rare-metal minerals. Attractive pieces are collected, though this example appears ordinary.
Geological facts
Pegmatites can host spectacular crystals of tourmaline, beryl, spodumene, and rare-earth minerals. Their crystals may range from centimeters to many meters in exceptional bodies.
Field identification & locations
Identify by visible coarse quartz, feldspar, and mica crystals; quartz scratches glass, while feldspar commonly shows cleavage and mica splits into thin sheets. Common worldwide in and around granite plutons, including Brazil, the United States, Canada, and Madagascar.
