metamorphic
Quartz (River Siltstone Quartzite Pebble)
Silicon Dioxide (SiO2)
Hardness: 7 on the Mohs scale. Color: Opaque light gray to white with possible blue-gray undertones. Luster: Dull or waxy (due to river weathering). Crystal structure: Hexagonal (trigonal), though not visible in this smooth, water-worn form. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 7 on the Mohs scale
- Luster
- Dull or waxy (due to river weathering)
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Physical properties
Hardness: 7 on the Mohs scale. Color: Opaque light gray to white with possible blue-gray undertones. Luster: Dull or waxy (due to river weathering). Crystal structure: Hexagonal (trigonal), though not visible in this smooth, water-worn form. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Over millions of years, heat and pressure fused the grains into quartzite. This specific specimen has been further shaped and polished by the mechanical action of water in a river or stream environment over thousands of years.
Uses & applications
Used in landscaping, construction aggregate, and as 'river rock' for garden decoration. Highly pure quartzite can be used to produce silicon metal or glass. In a tumbled form like this, it is often a starter piece for amateur rock collectors or used in decorative vase fillers.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. These water-worn river stones are often called 'sleeping stones' or 'spirit stones' in various cultures because of their smooth, calming tactile feel. They are remarkably durable and can survive hundreds of miles of transport in a riverbed.
Field identification & locations
Identify in the field by its hardness (it should easily scratch glass but cannot be scratched by a steel knife) and its smooth, rounded 'egg-like' shape caused by water erosion. Commonly found in riverbeds, glacial deposits, and coastal beaches globally. Collectors look for unique banding or internal fractures that catch the light.
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