metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on the Mohs scale, Color: Grey with subtle banding, Luster: Vitreous to greasy, Crystal structure: Trigonal (microcrystalline quartz grains), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
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Physical properties
Hardness: 7 on the Mohs scale, Color: Grey with subtle banding, Luster: Vitreous to greasy, Crystal structure: Trigonal (microcrystalline quartz grains), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure, typically in tectonic mountain-building events over millions of years
Uses & applications
Used in landscaping, construction aggregate, decorative stones, and road surfacing
Geological facts
Quartzite is extremely resistant to weathering and chemical breakdown, which is why it often survives long transport in rivers and oceans to become smooth, rounded pebbles
Field identification & locations
Can be identified in the field by its high hardness (scratches glass easily), lack of reaction to acid, and sugary texture visible on broken surfaces; commonly found in riverbeds, beaches, and glacial deposits
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