metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: White, off-white, light tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White, off-white, light tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, off-white, light tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, crystalline rock. The rounded shape indicates secondary weathering in a river or stream environment.
Uses & applications
Commonly used as high-quality aggregate in construction, road ballast, and decorative landscaping. High-purity quartzite are used to produce silica sand for glassmaking and silicon industrial products.
Geological facts
Quartzite is so tough that it often survives intense weathering that destroys other rocks, which is why it is frequently found as rounded river pebbles. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and lack of reaction to acid. It is commonly found in riverbeds, glacial tills, and ancient mountain belts globally.
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