igneous
Quartz on Feldspar
Silicon Dioxide (SiO2) with Potassium Feldspar (KAlSi3O8)
Hardness: 6-7 Mohs; Color: Smokey grey/tan and creamy white; Luster: Vitreous to dull; Crystal Structure: Trigonal/Monoclinic; Cleavage: None in quartz, two perfect planes in feldspar; SG: 2.5-2.7
- Hardness
- 6-7 Mohs
- Color
- Smokey grey/tan and creamy white
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Smokey grey/tan and creamy white; Luster: Vitreous to dull; Crystal Structure: Trigonal/Monoclinic; Cleavage: None in quartz, two perfect planes in feldspar; SG: 2.5-2.7
Formation & geological history
Formed in granitic pegmatites through the slow cooling of silica-rich magma deep within the Earth's crust, typically during the final stages of igneous crystallization.
Uses & applications
Industrial source of silica and alumina; used in ceramics, glassmaking, and frequently as mineral specimens for education and collecting.
Geological facts
Quartz and feldspar are the two most abundant minerals in the Earth's continental crust. This specific combination is the primary constituent of granite.
Field identification & locations
Identify by quartz's glassy, conchoidal fracture and the feldspar's blocky shape with flat cleavage faces. Common in mountain ranges and glacial deposits.
