metamorphic
River Stone (likely Quartzite or Sandstone)
Metamorphosed Quartz-rich Rock (SiO2)
Hardness: 7 (Mohs scale); Color: Brownish-tan with mottled patches; Luster: Dull to waxy when wet; Crystal structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture)
- Hardness
- 7 (Mohs scale)
- Color
- Brownish-tan with mottled patches
- Luster
- Dull to waxy when wet
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Brownish-tan with mottled patches; Luster: Dull to waxy when wet; Crystal structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the intense heat and pressure of burial (metamorphism) of quartz-rich sandstone. It has been weathered and rounded by fluvial action in a river or stream bed over thousands of years.
Uses & applications
Commonly used in landscaping, decorative ground cover, aquarium substrate, and as aggregate in construction and concrete.
Geological facts
River stones get their smooth, rounded shape through a process called abrasion, where water carries the stones and tumbles them against other rocks and sand in a riverbed.
Field identification & locations
Identify in the field by its rounded, smooth 'potato-like' shape and high hardness (cannot be scratched by a steel knife). Commonly found in current or ancient river valleys and beaches.
More like this
