metamorphic
Quartzite River Stone
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, gray, and cream with possible iron staining; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: ~2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, gray, and cream with possible iron staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, gray, and cream with possible iron staining; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: ~2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the quartz grains into a dense, interlocking matrix. This specific specimen has been further shaped by fluvial (river) erosion over thousands of years.
Uses & applications
Used in construction as road ballast, in landscaping as decorative river rock, and sometimes in glass manufacturing if the silica content is high enough.
Geological facts
Quartzite is so hard that when it breaks, the fracture goes through the quartz grains rather than around them, unlike its parent stone, sandstone.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and lack of reaction to acid. It is commonly found in riverbeds, glacial deposits, and mountain ranges where ancient sedimentary basins have been uplifted.
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