Smoky Quartz and Feldspar Pegmatite

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Grayish-black smoky quartz with tan/white feldspar and iron staining; Luster: Vitreous (glassy) to dull; Crystal structure: Hexagonal (quartz) and Monoclinic (feldspar); Specific gravity: ~2.6-2.7

Formation & Geological History

Formed during the final stages of a magma's crystallization, where high water content allows for the growth of large crystals in veins or dikes. Common in Precambrian or Paleozoic geological environments.

Uses & Applications

Used primarily for mineral collecting; quartz can be used in glassmaking and feldspar in ceramics. High-quality smoky quartz is used in jewelry.

Geological Facts

Pegmatites are famous for containing the largest crystals found on Earth. The dark 'smoky' color in the quartz crystals is often the result of natural irradiation of silicon dioxide crystals over millions of years.

Field Identification & Locations

Identify by looking for very large, interlocking crystalline grains (quartz, feldspar, mica) in a vein-like structure. Commonly found in mountainous regions with exposed granite basements.

Identified on: 4/22/2026

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