igneous
Smoky Quartz and Orthoclase Feldspar
Granitic Pegmatite (SiO2 + KAlSi3O8)
Hardness: 6-7 (Mohs scale), Color: Smoky grey/black and tan/pink peach, Luster: Vitreous to greasy, Crystal structure: Trigonal/Monoclinic, No cleavage in quartz/two planes at 90 degrees in feldspar.
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Smoky grey/black and tan/pink peach, Luster: Vitreous to greasy, Crystal structure: Trigonal/Monoclinic, No cleavage in quartz/two planes at 90 degrees in feldspar.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep within the Earth's crust, typically in pegmatite veins or plutonic intrusions during the late stages of magmatic crystallization.
Uses & applications
Commonly used as decorative stones, gemstones when high quality, and in crystal healing collections. Granitic components are also essential in high-end construction (granite countertops).
Geological facts
Smoky quartz gets its dark color from natural irradiation within the earth acting on aluminum impurities. Feldspar is the most abundant mineral group in the Earth's crust.
Field identification & locations
Identify by looking for the 'salt and pepper' or blotchy appearance of translucent grey quartz mixed with opaque, blocky feldspar. It is common in mountain ranges with exposed granite cores.
