metamorphic
Quartzite (Gold/Tan River Cobble)
Quartzite (composed primarily of crystalline SiO2)
Hardness: 7 on Mohs scale; Color: Tan, golden-brown, beige; Luster: Dull to vitreous; Crystal Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, golden-brown, beige
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, golden-brown, beige; Luster: Dull to vitreous; Crystal Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, often during mountain-building events. This specific specimen is a water-worn river cobble, rounded by fluvial erosion.
Uses & applications
Used in construction as crushed stone or road ballast, as a refractory material in industrial furnaces, and occasionally as decorative landscaping stone.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is one of the most durable and weather-resistant rocks on the Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness, granular 'sugary' texture on fresh breaks, and resistance to chemical weathering. Extremely common in riverbeds and glacial tills globally.
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