metamorphic
Quartzite Cobble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, grey, or off-white with localized iron staining; Luster: dull to vitreous; Texture: granoblastic with visible fused sand grains; Structure: massive and non-foliated.
- Hardness
- 7 on Mohs scale
- Color
- tan, grey, or off-white with localized iron staining
- Luster
- dull to vitreous
Identified More metamorphic →
Explore Quartzite Cobble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: tan, grey, or off-white with localized iron staining; Luster: dull to vitreous; Texture: granoblastic with visible fused sand grains; Structure: massive and non-foliated.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to extreme heat and pressure, typically during mountain-building events (orogeny). Rounded into cobbles by fluvial (river) or glacial transport over thousands of years.
Uses & applications
Commonly used in landscaping, road construction (as crushed aggregate), and occasionally as a refractory material in industrial furnaces due to high silica content.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel tools. It is one of the most physically durable and chemically resistant rocks found on Earth's surface.
Field identification & locations
Identify in the field by its hardness (will not scratch with a knife) and its grainy, sandpaper-like surface that nonetheless feels smooth due to water-wear; found abundantly in riverbeds and glacial tills.
More like this
