metamorphic
River Stone (Quartzite)
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: light grey to tan/brownish, Luster: dull to vitreous when polished, Crystal structure: granular/microcrystalline, Cleavage: none, Specific gravity: 2.6 - 2.8
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Physical properties
Hardness: 7 (Mohs scale), Color: light grey to tan/brownish, Luster: dull to vitreous when polished, Crystal structure: granular/microcrystalline, Cleavage: none, Specific gravity: 2.6 - 2.8
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This specific specimen has been further shaped by fluvial (river) erosion, which has smoothed and rounded its surface over centuries or millennia.
Uses & applications
Primary uses include landscaping, construction aggregate, and decorative garden pieces. Smooth stones are also used in massage therapy (hot stone massage) and for painting/crafting.
Geological facts
Quartzite is so durable that it can withstand intense weathering; because of its hardness, a piece of quartzite will scratch glass and even common steel pocketknife blades.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and its grainy, sugary appearance when broken. These are commonly found in riverbeds, glacial moraines, and beaches.
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