metamorphic
Quartzite Cobble
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Yellow-brown, tan, or rusty (due to iron oxidation); Luster: Non-foliated, sugary to vitreous; Structure: Massive; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Yellow-brown, tan, or rusty (due to iron oxidation)
- Luster
- Non-foliated, sugary 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 (Mohs scale); Color: Yellow-brown, tan, or rusty (due to iron oxidation); Luster: Non-foliated, sugary to vitreous; Structure: Massive; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic processes cause the quartz grains to recrystallize and fuse together. The yellow-brown exterior staining is common in cobbles found in riverbeds or glacial till due to limonite/iron oxide weathering.
Uses & applications
Primarily used in construction as crushed stone for road ballast, railroad beds, and asphalt. Harder varieties are used as industrial abrasives or for landscaping decorative stones.
Geological facts
Quartzite is so hard and dense that when it is broken, it fractures through the quartz grains rather than around them, distinguishing it from sandstone. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its lack of reaction to acid. Look for a dense, grainy texture that resembles sugar cubes under a magnifying glass. Commonly found in areas with ancient mountain belts or glacial deposits.
More like this
