Pegmatite with Smoky Quartz and Feldspar

Physical Properties

Hardness 6-7 (Mohs scale), colors ranging from white/tan matrix to dark smoky gray crystals, vitreous to pearly luster, massive to coarse-grained crystal structure, specific gravity 2.6-2.7

Formation & Geological History

Formed during the final stages of a magma's crystallization, usually in intrusive igneous environments where high water content allows for the growth of very large crystals. Often billions to hundreds of millions of years old.

Uses & Applications

Primary source of industrial minerals like quartz and feldspar; smoky quartz is used in jewelry and lapidary arts; high-quality specimens are valued by collectors.

Geological Facts

Pegmatites are famous for containing the largest crystals ever found on Earth, sometimes reaching many meters in length. They often concentrate rare elements like lithium, beryllium, and tantalum.

Field Identification & Locations

Identify by the exceptionally large grain size compared to surrounding granitic rocks. Look for the distinct glassy, dark appearance of smoky quartz embedded in a lighter, chalky or blocky feldspar matrix.

Identified on: 5/16/2026

Mode: Standard