metamorphic
Quartzite River Rock
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white, grey, and tan; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Off-white, grey, and tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white, grey, and tan; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped into a rounded, oblong form by water erosion in a high-energy fluvial environment.
Uses & applications
Commonly used as decorative landscaping stone, in construction aggregates, or as high-durability road ballast. Also used in the manufacturing of glass and ceramics.
Geological facts
Quartzite is so hard that it can scratch steel. This particular specimen is a 'river cobble', which means its smooth, elongated shape was carved over centuries or millennia by flowing water and collisions with other rocks.
Field identification & locations
Identify by its hardness (scratches glass), grainy texture similar to sandstone but more fused, and lack of reaction to acid. Often found in riverbeds, glacial deposits, and mountain ranges.
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