metamorphic
Quartzite pebble on Granite surface
Quartzite (small pebble) resting on polished Granite (Gneissic Granite countertop)
Hardness: 7 on Mohs scale; Color: Tan to light pinkish-brown (pebble), mottled cream, black, and quartz clear/gray (countertop background); Luster: Granular/dull on pebble, vitreous/polished on background; Cleavage: None (conchoidal to uneven fracture).
- Hardness
- 7 on Mohs scale
- Luster
- Granular/dull on pebble, vitreous/polished on background
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to light pinkish-brown (pebble), mottled cream, black, and quartz clear/gray (countertop background); Luster: Granular/dull on pebble, vitreous/polished on background; Cleavage: None (conchoidal to uneven fracture).
Formation & geological history
Quartzite forms through the metamorphism of quartz sandstone under high heat and pressure, recrystallizing quartz grains into a interlocking network. Granite forms from slow crystallization of silica-rich magma below the Earth's surface.
Uses & applications
Quartzite is used for railway ballast, decorative stone, construction aggregate, and dimension stone. Polished granite/gneiss is widely used for building facades, monuments, and residential countertops.
Geological facts
Quartzite is extremely tough and durable, often resisting weathering far better than surrounding rocks. The underlying granite slab features prominent biotite mica, potassium feldspar, and quartz grains.
Field identification & locations
Identify quartzite by its granular sugar-like texture that fractures across individual sand grains rather than around them. Found globally in mountainous regions and riverbeds as eroded gravel.
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