metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: Tan, brown, or grey with iron staining. Luster: Dull to vitreous (waxy). Structure: Granular, non-foliated. Specific gravity: 2.6-2.7. Highly resistant to physical weathering.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, or grey with iron staining
- Luster
- Dull to vitreous (waxy)
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, brown, or grey with iron staining. Luster: Dull to vitreous (waxy). Structure: Granular, non-foliated. Specific gravity: 2.6-2.7. Highly resistant to physical weathering.
Formation & geological history
Formed from the metamorphism of quartz sandstone under heat and pressure, causing recrystallization. This specific specimen has been further shaped by fluvial (river) erosion, which has smoothed and rounded its edges over thousands of years.
Uses & applications
Commonly used as decorative garden stone, in landscaping, as railroad ballast, or crushed for use in road construction. It is too hard for most carving but valued for durability.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caprocks of mountains. River-worn specimens like this are often found far from their original source, carried downstream by high-energy water environments.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by steel) and smooth, rounded water-worn texture. Commonly found in riverbeds, glacial deposits, and beaches. For collectors, look for unique colors or surface patterns.
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