metamorphic
Quartzite
Metaquartzite (predominantly SiO2)
AI-generated identification · may be incorrectHardness 7 on the Mohs scale; light gray to tan or beige with subtle iron staining; dull to vitreous or sugary luster; granoblastic texture with tightly interlocked quartz grains; no cleavage; specific gravity roughly 2.65.
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Physical properties
Hardness 7 on the Mohs scale; light gray to tan or beige with subtle iron staining; dull to vitreous or sugary luster; granoblastic texture with tightly interlocked quartz grains; no cleavage; specific gravity roughly 2.65.
Formation & geological history
Formed by intense heat and pressure recrystallizing quartz-rich sandstone or chert during regional or contact metamorphism.
Uses & applications
Commonly crushed for construction aggregate, railway ballast, riprap, architectural facing stone, and manufacturing silicon metal or silica glass.
Geological facts
Because quartzite breaks across individual sand grains rather than around them, it is exceptionally tough and resistant to chemical and physical weathering, often forming the spines of long mountain ridges.
Field identification & locations
Identified in the field by its high hardness (easily scratches glass and steel), lack of reaction to dilute hydrochloric acid, sugary granular sheen on fresh breaks, and typical river-worn or glaciated pebble weathering.
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