metamorphic
Quartzite Cobble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-yellow, translucent to opaque; Luster: Vitreous/waxy; Structure: Granular/mylonitic; Cleavage: None; SG: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-yellow, translucent to opaque
- Luster
- Vitreous/waxy
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-yellow, translucent to opaque; Luster: Vitreous/waxy; Structure: Granular/mylonitic; Cleavage: None; SG: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. This specific specimen is a river-rounded cobble, likely of Paleozoic or Precambrian age, weathered and smoothed by water transport.
Uses & applications
Used as decorative stone in landscaping, as a railway ballast, in construction as crushed stone, and sometimes as a tool (hammerstone) by prehistoric humans.
Geological facts
Quartzite is so hard and chemically stable that it often survives in the geological record long after other rocks have eroded away, forming prominent ridges and peaks.
Field identification & locations
Identify in the field by its inability to be scratched by steel, its sugary grain texture on a fresh break, and its water-worn, smooth exterior if found in rivers. Found globally in mountainous or glaciated regions.
More like this
