igneous
Pegmatitic granite
Coarse-grained granitic rock, chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectHardness about 6–7 Mohs; cream, pink, gray, and black; vitreous to pearly luster with very coarse interlocking crystals. Quartz is hard and glassy, feldspar commonly shows cleavage, and mica occurs as dark flaky plates.
Identified More igneous →
Explore Pegmatitic granite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6–7 Mohs; cream, pink, gray, and black; vitreous to pearly luster with very coarse interlocking crystals. Quartz is hard and glassy, feldspar commonly shows cleavage, and mica occurs as dark flaky plates.
Formation & geological history
Forms when silica-rich magma cools slowly, commonly in the margins of granite plutons; pegmatites may crystallize during the late Paleozoic to Cenozoic, depending on locality.
Uses & applications
Used as decorative stone, countertops, aggregate, and a source of feldspar, quartz, mica, and occasionally lithium, beryl, or tourmaline. Attractive specimens are collected.
Geological facts
The unusually large crystals result from water- and volatile-rich residual magma, which allows rapid ion movement during crystallization.
Field identification & locations
Identify it by its visibly oversized quartz and feldspar crystals, pink or white feldspar, and dark mica; it is commonly found in granite terrains and mineralized veins worldwide. Acid testing is unnecessary; quartz should scratch glass.
