metamorphic
River Quartzite Spheroid
Recrystallized Orthoquartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, cream, or light brown with iron staining; Luster: Dull to waxy; Structure: Granoblastic, non-foliated; Cleavage: None; Specific Gravity: 2.63 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, cream, or light brown with iron staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, cream, or light brown with iron staining; Luster: Dull to waxy; Structure: Granoblastic, non-foliated; Cleavage: None; Specific Gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to fuse. The rounded shape indicates significant hydraulic erosion in a river or coastal environment over thousands of years.
Uses & applications
Commonly used as abrasive media, decorative landscaping stones, or in high-silica construction materials. Small smooth specimens are often kept as pocket stones or river-worn curiosities.
Geological facts
Quartzite is so tough that it often outlasts the mountains it was formed in, becoming the primary component of many river bed gravels. Its signature hardness means it will easily scratch glass.
Field identification & locations
Identify by its ability to scratch glass and its grainy, 'sugary' texture seen under a hand lens. Commonly found in glacio-fluvial deposits, riverbeds, and gravel pits worldwide.
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