metamorphic
Quartzite (River Pebble)
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale (scratches glass). Color: Tan, off-white, or brownish. Luster: Vitreous to dull. Crystal structure: Hexagonal/Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: Approximately 2.65.
- Hardness
- 7 on Mohs scale (scratches glass)
- Color
- Tan, off-white, or brownish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale (scratches glass). Color: Tan, off-white, or brownish. Luster: Vitreous to dull. Crystal structure: Hexagonal/Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: Approximately 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to heat, pressure, and chemical activity of metamorphism. This specific specimen has been rounded by fluvial erosion in a river or stream environment.
Uses & applications
Industrial use as a source of silica, railway ballast, and decorative landscaping stone. Polished versions are used in jewelry and home decor.
Geological facts
Quartzite is one of the most physically and chemically resistant rocks found at the Earth's surface. It often survives long after the surrounding softer rocks have eroded away.
Field identification & locations
Identify in the field by its extreme hardness and lack of reaction to acid. Commonly found in riverbeds, glacial deposits, and mountain ranges. It will typically scratch steel and glass.
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