metamorphic
Quartzite with Milky Quartz Vein
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: White, grey, and tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoisdal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- White, grey, and tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, grey, and tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoisdal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. The white vein suggests secondary hydrothermal activity where silica-rich fluids filled fractures.
Uses & applications
Primarily used as crushed stone for road construction, railroad ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the peaks of ridges and mountains. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and grainy, sandpaper-like texture that unlike sandstone, breaks through the quartz grains rather than around them. Common in metamorphic belts worldwide.
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