metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: grayish-white to tan, Luster: vitreous to dull, Crystal structure: Trigonal (granular texture), Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: grayish-white to tan, Luster: vitreous to dull, Crystal structure: Trigonal (granular texture), Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used in construction as crushed stone or decorative facing, in metallurgy as a source of silica, and as a durable material for countertops.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in mountainous areas, forming prominent ridges and peaks. It is the hardest common rock.
Field identification & locations
Identified by its ability to scratch glass and its granular, sugary appearance. Unlike sandstone, it will break through the sand grains rather than around them.
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