metamorphic
Quartzite River Rock (with iron staining)
Metamorphosed Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: Brown/Grey exterior with orange/yellow iron leaching, Luster: Dull to vitreous, Crystal Structure: Hexagonal (massive/granular), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.7.
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Physical properties
Hardness: 7 (Mohs scale), Color: Brown/Grey exterior with orange/yellow iron leaching, Luster: Dull to vitreous, Crystal Structure: Hexagonal (massive/granular), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen shows water-worn rounding, indicating it was transported by a river or stream over a long geological period.
Uses & applications
Used in construction as crushed stone or road ballast; in industry for silica manufacturing; commonly used in decorative landscaping and as aquarium stones.
Geological facts
Quartzite is so touch that it will break through the quartz grains themselves rather than around them. The yellowish-orange patch on this specimen is likely limonite or goethite staining caused by the oxidation of iron-bearing minerals within the rock.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel pocket knife) and its grainy, sandpaper-like texture that remains visible despite water erosion. Found globally in ancient mountain belts and riverbeds.
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