metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, orange, or white; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.6.
- Hardness
- 7 on Mohs scale
- Color
- tan, orange, or white
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, orange, or white; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.6.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize quartz grains into a dense, interlocking matrix. Found in orogenic belts worldwide.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in flooring or countertops. Occasionally used as a gemstone when color is vibrant.
Geological facts
Quartzite is so tough that it often outlasts neighboring rocks during erosion, frequently forming the peaks of ridges and mountains. It is more resistant to weathering than the sandstone it originated from.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade) and grainy sugary texture. Commonly found in mountainous regions or glacial till. Collectors look for unique colorations caused by impurities.
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