metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with yellow, pink, or red tints due to iron oxides; Luster: vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: none, breaks with a conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with yellow, pink, or red tints due to iron oxides; Luster: vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: none, breaks with a conchoidal fracture.
Formation & geological history
Quartzite forms from the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. These rocks can date back several billion years in some shield areas.
Uses & applications
Used as a decorative stone in construction (countertops, flooring, wall cladding), as railway ballast, and in the production of glass and silicon-based materials.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges and hills. It is harder and more durable than the parent sandstone from which it originated.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its granular, sugary texture. It is commonly found in mountain belts and areas of uplift where ancient sedimentary basins were metamorphosed.
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