metamorphic
Quartzite
Quartzite (primarily SiO2)
AI-generated identification · may be incorrectHardness: ~7 on Mohs scale; Color: purplish-gray, reddish-brown, to pinkish; Luster: vitreous to dull/sugary; Texture: granoblastic (interlocking quartz grains); Fracture: conchoidal to irregular, breaks directly across grains rather than around them; Specific Gravity: ~2.65
- Hardness
- ~7 on Mohs scale
- Color
- purplish-gray, reddish-brown, to pinkish
- Luster
- vitreous to dull/sugary
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Physical properties
Hardness: ~7 on Mohs scale; Color: purplish-gray, reddish-brown, to pinkish; Luster: vitreous to dull/sugary; Texture: granoblastic (interlocking quartz grains); Fracture: conchoidal to irregular, breaks directly across grains rather than around them; Specific Gravity: ~2.65
Formation & geological history
Formed through regional or contact metamorphism of quartz-rich sandstone subjected to intense heat and tectonic pressure, causing original sand grains and silica cement to recrystallize into a dense, durable mosaic.
Uses & applications
Commonly used as crushed stone for railway ballast, construction aggregate, riprap, architectural building stone, and decorative landscaping rock.
Geological facts
Quartzite is one of the most physically durable and chemically resistant rocks on Earth's surface, frequently forming prominent ridges, hogbacks, and resistant mountain caps.
Field identification & locations
Identify in the field by checking that it readily scratches glass and knife steel, has a sparkling sugary texture of fused quartz grains, and fractures through the quartz grains rather than along grain boundaries like sandstone. Widely distributed globally in ancient metamorphic terrains, riverbeds, and glacial deposits.
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