metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, white, or grey with iron staining; Luster: Dull to vitreous; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, white, or grey with iron staining
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, white, or grey with iron staining; Luster: Dull to vitreous; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed from quartzose sandstone that underwent intense heat and pressure (metamorphism). This specific specimen has been further shaped by fluvial erosion in a river or stream environment.
Uses & applications
Construction aggregate, decorative landscaping, historical use as stone tools, and industrial use in glass making or as a source of silica.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identify in the field by its high hardness (it will easily scratch glass) and lack of reaction to acid. Often found in riverbeds, glacial tills, and mountain ranges. Collectors look for smooth, well-rounded shapes.
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