metamorphic
Jasper-bearing Quartzite River Cobble
Tectonized Quartzite with Iron-Oxide (Hematite/Limonite) Veining
Hardness: 6.5-7 (Mohs scale); Color: Gray-green matrix with a distinct reddish-brown jasper or iron-oxide vein; Luster: Dull to waxy; Texture: Fine-grained, smoothed by water erosion.
- Hardness
- 6
- Luster
- Dull to waxy
Identified More metamorphic →
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Gray-green matrix with a distinct reddish-brown jasper or iron-oxide vein; Luster: Dull to waxy; Texture: Fine-grained, smoothed by water erosion.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. The reddish band is a result of hydrothermal fluids rich in iron silica filling a fracture late in the rock's geological history. It has been rounded and polished by high-energy river transport.
Uses & applications
Used primarily as decorative garden stone, aquarium gravel, or lapidary material for tumbling and polishing.
Geological facts
River rocks like this are often 'travelers' that have been moved hundreds of miles from their original mountain source by glacial or fluvial processes. The red vein is likely hematite-stained microcrystalline quartz (jasper).
Field identification & locations
Identify by its hardness (it will scratch glass) and the presence of a distinct mineral vein. Common in alluvial deposits, riverbeds, and glacial till. Collectors look for 'veined' or 'lightning' patterns like this for tumbling.
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