metamorphic
Quartzite / Sandstone
Quartzite (SiO2)
Mohs hardness of 6.5 to 7. Light beige, tan, grey, and off-white in color with dull to vitreous luster. Granular, sugary texture composed primarily of fused quartz grains, crossed by thin fracture lines. Non-porous and very durable.
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Physical properties
Mohs hardness of 6.5 to 7. Light beige, tan, grey, and off-white in color with dull to vitreous luster. Granular, sugary texture composed primarily of fused quartz grains, crossed by thin fracture lines. Non-porous and very durable.
Formation & geological history
Formed from quartz-rich sandstone through heat, pressure, and regional metamorphism, or heavy silica cementation (orthoquartzite). Commonly weathered into smooth cobbles by river or wave action.
Uses & applications
Widely used in construction as crushed stone, ballast, building stone, decorative landscaping rocks, and flagstone. Highly valued for its hardness and weather resistance.
Geological facts
Unlike sandstone, quartzite breaks through its component quartz grains rather than around them, resulting in a smooth fracture surface despite its granular appearance.
Field identification & locations
Identified by its sugary granular texture, extreme hardness (scratches glass), and resistance to acid. Commonly found in riverbeds, glacial tills, and mountainous metamorphic terrains.
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