metamorphic
Quartzite Cobble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellowish, or light brown; Luster: Vitreous to dull when weathered; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellowish, or light brown
- Luster
- Vitreous to dull when weathered
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellowish, or light brown; Luster: Vitreous to dull when weathered; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen has been rounded into a 'cobble' shape through fluvial (river) or glacial transport and abrasion over thousands to millions of years.
Uses & applications
Used as decorative garden stone, road ballast, and in construction as a high-strength aggregate. High-purity quartzite is used to produce silica for glassmaking and electronics.
Geological facts
Quartzite is so hard that it will scratch glass and steel. Most 'river rocks' found in landscaping that are tan or white are actually rounded quartzite or high-quartz sandstone cobbles.
Field identification & locations
Identify in the field by its extreme hardness and 'sugary' texture on a fresh break. Commonly found in riverbeds, glacial tills, and desert pavements across globally distributed metamorphic terrains.
More like this
