metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellow-orange (due to iron staining), and white; Luster: Vitreous to dull; Structure: Granular/Massive; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellow-orange (due to iron staining), and white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellow-orange (due to iron staining), and white; Luster: Vitreous to dull; Structure: Granular/Massive; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. High heat and pressure reciprocal to tectonic activity cause individual quartz grains to recrystallize and fuse together. This specimen shows significant rounding from fluvial (river) erosion over thousands of years.
Uses & applications
Commonly used in landscaping, decorative ground cover, and as an aggregate in high-strength concrete. Higher quality specimens are used for stone tumbling and lapidary practice.
Geological facts
Quartzite is so tough that it often survives the intense physical weathering of river transport while softer rocks are ground to sand. It is often harder than the steel of a pocket knife, which is a common way to distinguish it from similar-looking limestone.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, granular appearance on fresh breaks. Found globally in riverbeds, glacial moraines, and ancient sedimentary basins. Collectors often look for iron-stained versions like this for their warm colors.
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