metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan with iron staining, Luster: dull to vitreous, Crystal structure: granular/interlocking quartz grains, Cleavage: none, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan with iron staining, Luster: dull to vitreous, Crystal structure: granular/interlocking quartz grains, Cleavage: none, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen shows significant rounding due to fluvial (river) erosion over many years.
Uses & applications
Construction aggregate, railway ballast, decorative landscaping stones, and occasionally as a source of silica for industrial manufacturing.
Geological facts
Quartzite is so hard that it can scratch glass and steel. This specific specimen displays a prominent iron-oxide stain vein, likely formed by mineral-rich water seeping through cracks during its geological history.
Field identification & locations
Identify by its hardness (will scratch a glass bottle) and its graininess which resembles sugar but cannot be broken off easily. Extremely common in riverbeds and glacial deposits globally.
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