metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellowish as seen here; Luster: vitreous or dull when weathered; Texture: granular, crystalline; Fracture: conchoidal or irregular
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or yellowish as seen here
- Luster
- vitreous or dull when weathered
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellowish as seen here; Luster: vitreous or dull when weathered; Texture: granular, crystalline; Fracture: conchoidal or irregular
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into a locked mosaic. This specific specimen has been Rounded by river or beach water erosion.
Uses & applications
Used in construction as road ballast, gravel, and building stone. Highly pure quartzite is used to produce ferrosilicon and industrial silica sand. Smooth specimens are popular for landscape gardening.
Geological facts
Quartzite is extremely resistant to weathering and chemical erosion, often outlasting the rocks that surround it. The dark 'X' pattern in this specimen is likely a micro-fracture or vein filled with dark minerals or iron oxides.
Field identification & locations
Identify by its ability to scratch glass (high hardness) and its lack of reaction to acid. It is commonly found in mountain ranges or as water-worn pebbles in glacial till and riverbeds worldwide.
