metamorphic
Riverstone (Quartzite Pebble)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, grey, and cream with possible iron staining; Luster: Dull to waxy; Texture: Granular and smoothed by water/abrasion; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, grey, and cream with possible iron staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, grey, and cream with possible iron staining; Luster: Dull to waxy; Texture: Granular and smoothed by water/abrasion; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from quartz-rich sandstone subjected to high heat and pressure (metamorphism), causing quartz grains to recrystallize. This specific specimen was later rounded by fluvial (river) or glacial transport.
Uses & applications
Used as decorative landscaping stone, construction aggregate, and in some cultures as tools (hammerstones) or for lapidary tumbling.
Geological facts
Quartzite is so tough that it often survives multiple cycles of erosion and mountain building, which is why it is frequently found as rounded cobbles in riverbeds far from its source.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, crystalline surface texture under a lens. It lacks the distinct layering of sandstone because the grains were fused together.
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