metamorphic
Quartzite (River Stone)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, pinkish-white, gray; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Grainy, sand-like texture visible under magnification.
- Hardness
- 7 on Mohs scale
- Color
- tan, pinkish-white, gray
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, pinkish-white, gray; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Grainy, sand-like texture visible under magnification.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specimen is a water-worn river cobble.
Uses & applications
Used in construction as crushed stone for road beds, railway ballast, and as a decorative landscaping stone. High-purity quartzite is used to produce glass and silicon.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, forming prominent ridges and hills. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identified by its sugary texture and extreme hardness (cannot be scratched by a knife). Commonly found in riverbeds, glacial deposits, and mountain ranges globally.
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