igneous
Biotite-rich granite (granite pegmatitic rock)
Granite, primarily quartz (SiO₂), feldspars, and biotite mica
AI-generated identification · may be incorrectCoarse-grained, speckled gray, cream, pink, and black; vitreous quartz, pearly mica, and feldspar luster. Hardness is about 6–7 for the main mass; crystals are interlocking, with mica showing perfect basal cleavage and granite lacking a consistent cleavage.
Identified More igneous →
Explore Biotite-rich granite (granite pegmatitic rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse-grained, speckled gray, cream, pink, and black; vitreous quartz, pearly mica, and feldspar luster. Hardness is about 6–7 for the main mass; crystals are interlocking, with mica showing perfect basal cleavage and granite lacking a consistent cleavage.
Formation & geological history
Slow cooling of silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic plutonic activity; the specimen’s exact age cannot be determined visually.
Uses & applications
Used widely as dimension stone, countertops, monuments, aggregate, and paving; attractive pieces are collected, though this rough specimen has modest commercial value.
Geological facts
The pink tones typically come from potassium feldspar, gray translucent grains from quartz, and black reflective flakes from biotite. Its coarse texture records very slow underground cooling.
Field identification & locations
Common worldwide, including India, Brazil, Scandinavia, Canada, and the United States. Identify it by visible interlocking quartz, feldspar, and dark mica crystals; a steel file generally scratches feldspar only weakly and not quartz.
