metamorphic
Quartzite
SiO2 (Crystalline Quartz)
Hardness: 7 on Mohs scale; Color: Tan, brown, or pinkish due to iron oxide impurities; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, or pinkish due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, or pinkish due to iron oxide impurities; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen appears water-worn, likely sourced from a riverbed or coastal environment where it was tumbled over long periods.
Uses & applications
Commonly used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce glass and silica-based products.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges or hills known as 'monadnocks.' It breaks across its grain/quartz grains rather than around them, unlike sandstone.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its crystalline, sugary appearance on a fresh break. It is commonly found in ancient mountain belts and river deposits.
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