metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs); Color: Tan, beige, white, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs)
- Color
- Tan, beige, white, or yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs); Color: Tan, beige, white, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. Often found as rounded pebbles in riverbeds or beaches due to water erosion.
Uses & applications
Used as a construction aggregate, for railway ballast, in the manufacturing of glass and ceramics, and occasionally as decorative landscaping stones.
Geological facts
Quartzite is so tough that it often survives intense mechanical weathering better than most other rocks, leading to the formation of prominent ridges in mountain ranges.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, crystalline texture where broken. Commonly found in areas with ancient sedimentary basins that have undergone tectonic compression.
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