metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: Reddish-brown to tan, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Reddish-brown to tan, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. This specimen has been rounded by fluvial or beach erosion.
Uses & applications
Used as a decorative landscape stone, construction aggregate, and in high-purity forms for glass manufacturing or as a refractory material.
Geological facts
Quartzite is so tough that it often survives multiple cycles of erosion, outlasting the source mountains from which it came. It is harder than steel and will scratch glass easily.
Field identification & locations
Identify by its hardness (will scratch a knife blade) and interlocking crystalline texture. Commonly found in riverbeds, glacial tills, and ancient mountain belts like the Appalachians or the Alps.
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