metamorphic
Quartzite Cobble
Quartzite
Hardness: 7 on Mohs scale; Color: Grayish-white with yellow-brown staining; Luster: Vitreous to dull; Structure: Granular/Granoblastic; Streak: White; Heavily weathered and rounded surface.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with yellow-brown staining
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with yellow-brown staining; Luster: Vitreous to dull; Structure: Granular/Granoblastic; Streak: White; Heavily weathered and rounded surface.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to high heat and pressure, typically during mountain-building events. This specimen has been further shaped by fluvial (water) erosion into a river cobble.
Uses & applications
Commonly used as crushed stone for road construction, railroad ballast, and decorative landscaping. High-purity quartzite is used in glass making and electronics.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. Many river stones like this one have been transported hundreds of miles from their original source outcrop by ancient glacial or river systems.
Field identification & locations
Identify by its hardness (cannot be scratched by a knife) and its grainy, sugary look on a fresh break. They are frequently found in riverbeds, glacial tills, and beaches.
