metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white, yellowish-tan; Luster: Vitreous to dull; Structure: Granoblastic (interlocking quartz grains); Cleavage: None; Grains are fused and do not rub off like sandstone.
- Hardness
- 7 on Mohs scale
- Color
- Off-white, yellowish-tan
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white, yellowish-tan; Luster: Vitreous to dull; Structure: Granoblastic (interlocking quartz grains); Cleavage: None; Grains are fused and do not rub off like sandstone.
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. This specimen shows significant rounding and smoothing from fluvial (river) or glacial transport.
Uses & applications
Crushed stone for road construction, railway ballast, and as a raw material in the glass and ceramic industries. Smooth pebbles are often used in decorative landscaping and aquariums.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, remaining as resistant ridges or rounded river stones like this one. It is often harder than the steel of a pocket knife.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its sugary, crystalline texture that does not rub off into sand. Commonly found in riverbeds, glacial tills, and mountainous regions worldwide.
