metamorphic
Quartzite
Metamorphosed Sandstone (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: dirty white to light tan; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Granular texture.
- Hardness
- 7 on Mohs scale
- Color
- dirty white to light tan
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: dirty white to light tan; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Granular texture.
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, hard rock. Typically found in mountain belts and Precambrian shields.
Uses & applications
Used as a decorative stone in landscaping, a source of silica for glass making, in construction as crushed stone for road ballast, and for high-durability countertops.
Geological facts
Quartzite is so tough that it often survives intense erosion to form the crests of mountain ridges. Unlike sandstone, which breaks around its grains, quartzite breaks through its grains due to the complete fusion of quartz during metamorphism.
Field identification & locations
Identify it by its extreme hardness (it will easily scratch glass) and lack of reaction to acid. It is commonly found in gravel pits, riverbeds, or as outcroppings in hilly terrains. Collectors should look for rare colored variants like pink or green.
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