metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, rusty brown, or orange-red due to iron oxide staining; Luster: Dull to waxy; Texture: Granular, sugary texture when broken; Cleavage: None (conchoidal fracture).
- Hardness
- 7 (Mohs scale)
- Color
- Tan, rusty brown, or orange-red due to iron oxide staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, rusty brown, or orange-red due to iron oxide staining; Luster: Dull to waxy; Texture: Granular, sugary texture when broken; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. These specific specimens are water-worn, having been tumbled and rounded in a river or fluvial environment over thousands of years.
Uses & applications
Used primarily in landscaping, decorative ground cover, construction aggregate, and as 'river stone' for architectural accents.
Geological facts
Quartzite is so hard that it can often cut through glass and is significantly tougher than its parent sandstone. The rounded shape is a result of hydraulic action and abrasion in moving water.
Field identification & locations
Identify by its hardness (it will scratch a steel knife) and its rounded, smooth cobble shape. Often found in riverbeds, glacial deposits, and sedimentary basins. Common in areas with ancient mountain-building history.
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