metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, yellow, or off-white; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.6-2.7. Extremely hard and resistant to scratching.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, yellow, or off-white
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, yellow, or off-white; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.6-2.7. Extremely hard and resistant to scratching.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure caused the original sand grains to recrystallize and fuse together. This specific specimen has been rounded by fluvial (river) or coastal erosion.
Uses & applications
Commonly used as decorative landscaping rock, track ballast in railroads, and as a raw material in the manufacturing of glass and ceramics due to its high silica content.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, leading to the formation of prominent ridges and peaks in mountainous terrains.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and its sugary, crystalline texture when broken. Commonly found in riverbeds, glacial deposits, and mountain outcrops. Use a steel file to test hardness; quartzite will not be scratched by steel.
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