metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellow, or grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellow, or grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellow, or grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen shows significant rounding and smoothing from fluvial (river) or glacial transport.
Uses & applications
Used in construction as crushed stone or road ballast, as a refractory material in glassmaking, and in landscaping or decorative masonry.
Geological facts
Quartzite is so hard and durable that it often survives long-distance transport in rivers where softer rocks break down, resulting in the smooth cobble shape seen here.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sandpaper-like surface texture despite being smooth to the touch. It lack the distinct layers found in its parent sandstone.
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