igneous
Feldspar (Granite Pegmatite matrix)
Potassium Feldspar (KAlSi3O8) / Quartz Mixture
Mohs hardness 6 to 6.5 for feldspar and 7 for quartz. Color ranges from buff-tan, beige, pinkish-brown to off-white. Vitreous to dull earth luster. Blocky cleavage planes visible along fracture surfaces. Specific gravity approximately 2.56-2.65.
Identified More igneous →
Explore Feldspar (Granite Pegmatite matrix) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness 6 to 6.5 for feldspar and 7 for quartz. Color ranges from buff-tan, beige, pinkish-brown to off-white. Vitreous to dull earth luster. Blocky cleavage planes visible along fracture surfaces. Specific gravity approximately 2.56-2.65.
Formation & geological history
Formed via the slow crystallization of magma deep underground, typically within pegmatite veins or intrusive igneous rock bodies. Slow cooling allows coarse grains of feldspar, quartz, and minor mica minerals to form large visible crystals.
Uses & applications
Used extensively as a source of feldspar for ceramics, glassmaking, and industrial abrasives. Raw specimens are collected by geology enthusiasts for study and display.
Geological facts
Potassium feldspars like orthoclase and microcline make up more than half of the Earth's crust by weight. This specimen shows classic blocky fracture surfaces characteristic of feldspar mixed with quartz.
Field identification & locations
Identified by its buff to pinkish color, distinct blocky cleavage planes that reflect light, and hardness that easily scratches glass (6+). Commonly found in continental crust areas, mountain cores, and pegmatite districts globally.
