metamorphic
Quartz River Cobble (Yellow Jasper/Quartzite variant)
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or yellowish-brown; Luster: Waxy to dull; Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or yellowish-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or yellowish-brown; Luster: Waxy to dull; Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the regional metamorphism of quartz-rich sandstone. It has been subsequently eroded and shaped into a smooth, rounded 'cobble' or 'pebble' through long-term fluvial (river) transport over thousands of years.
Uses & applications
Commonly used as decorative landscaping stone, in construction as aggregate, or as tumble-polishing material for hobbyist lapidary collectors.
Geological facts
River stones like this owe their smooth texture to the 'tumbling' effect of water currents. Quartzite is one of the most durable and weather-resistant rocks on the Earth's surface, often outlasting the mountain ranges it originated from.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its smooth, rounded 'potato' shape from water erosion. Found in almost any active or prehistoric riverbed or glacial deposit.
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