metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White, grey, with iron staining (yellow/brown); Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, breaks with conchoidal or irregular fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White, grey, with iron staining (yellow/brown)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, grey, with iron staining (yellow/brown); Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, breaks with conchoidal or irregular fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize and fuse into a solid rock mass. This specimen shows water-worn rounding, likely from a fluvial or coastal environment.
Uses & applications
Used primarily as construction aggregate, railway ballast, and in some cases as a decorative stone in landscaping or as a source of silica for glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the caps of hills and ridges. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identify in the field by its high hardness (it will easily scratch glass) and its sugary, crystalline texture on a fresh break. It lacks the grainy feel of sandstone because the boundaries between grains have fused.
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