River Rock (Quartz-rich Gravel)
Silicon Dioxide (Quartz var. Chalcedony with impurities) · Mineral Specimen / Decorative Stone
Crystal System
Trigonal (microcrystalline); habit is typically rounded and water-worn
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (predominantly)
Formation Process
Sedimentary/Alluvial; formed through the erosion and transport of parent rock via water flow
About This Crystal
The stones in the foreground are multi-colored, sub-rounded to sub-angular pebbles. They display a range of earthy tones (grey, tan, brown) with a matte to waxy luster.
Physical Characteristics
Colors range from light grey to dark brown; streak is white; no cleavage visible; conchoidal to uneven fracture; specific gravity ~2.65; non-fluorescent.
Optical Properties
Opaque to translucent; no significant optical phenomena like asterism or chatoyancy in this grade of material.
Hardness & Durability
Origin Region
Ubiquitous world-wide; typically found in fluvial (river) or glacial deposits
Hardness & Durability
Mohs hardness of 7; high toughness and durability; resistant to chemical weathering.
Care & Maintenance
Hardy material; can be cleaned with water and mild detergent; resistant to sunlight and most household chemicals.
Rarity & Value
Very Common; low commercial value; typically sold by the ton for landscaping or industrial use.
Special Characteristics
Tumbled and smoothed by natural river action (natural abrasion) rather than mechanical tumblers.
Lore & History
Used since the Stone Age for tools and construction. Culturally associated with grounding and the element of Earth.