metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: Grey, white, or tan with translucent patches; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Specific gravity: 2.6-2.7. Shows a granular, sandpaper-like texture when broken.
- Hardness
- 7 on Mohs scale
- Color
- Grey, white, or tan with translucent patches
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grey, white, or tan with translucent patches; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Specific gravity: 2.6-2.7. Shows a granular, sandpaper-like texture when broken.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, often in orogenic (mountain-building) belts.
Uses & applications
Used as a decorative stone in landscaping, a flux in metallurgy, in the manufacturing of glass and ceramics, and as a durable material for countertops and construction aggregates.
Geological facts
Unlike sandstone, which breaks around its individual grains, quartzite is so strongly fused that it breaks right through the quartz grains themselves. This specimen shows water-worn rounding, likely from river transport.
Field identification & locations
Identify in the field by its superior hardness (it will easily scratch glass or steel) and its lack of reaction to acid. Often found in riverbeds, glacial tills, and mountainous regions.
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