metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, yellow, or white (iron staining creates the yellow/orange hue). Luster: Vitreous to dull. Crystal structure: Hexagonal/Trigonal (microcrystalline). No cleavage, conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, yellow, or white (iron staining creates the yellow/orange hue). Luster: Vitreous to dull. Crystal structure: Hexagonal/Trigonal (microcrystalline). No cleavage, conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the quartz grains into a dense, interlocking mosaic. This specimen appears to be a water-worn river pebble.
Uses & applications
Commonly used as crushed stone for road construction, railway ballast, and as a decorative landscaping stone. High-purity quartzite is used to produce silica sand for glass making.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers much more slowly than surrounding rocks.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass and steel) and its sugary, crystalline texture. Found globally in metamorphic belts and as pebbles in riverbeds.
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