metamorphic
Quartzite
Quartzite (composed primarily of Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with tan or pinkish tints; Luster: vitreous to dull; Crystal structure: interlocking mosaic of quartz grains; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, often with tan or pinkish tints
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with tan or pinkish tints; Luster: vitreous to dull; Crystal structure: interlocking mosaic of quartz grains; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the original sand grains to recrystallize and fuse together, eliminating most pore space.
Uses & applications
Extensively used in construction as crushed stone for road gravel and rail ballast, as dimension stone for flooring and wall cladding, and as a source of silica in glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming prominent ridges and peaks. It is sometimes mistaken for marble, but can be distinguished by its superior hardness.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. It typically breaks across the grains rather than around them, unlike sandstone. Common in mountain belts globally.
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