metamorphic
Quartzite Pebble
Metamorphosed Quartz Arenite (SiO2)
Mohs hardness: 7. Color: off-white to yellowish-tan with iron staining. Luster: dull to vitreous. Crystal structure: trigonal (microcrystalline). Texture: grainy, non-foliated, water-worn. Specific gravity: 2.63-2.65.
- Hardness
- 7
- Color
- off-white to yellowish-tan with iron staining
- Luster
- dull to vitreous
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Physical properties
Mohs hardness: 7. Color: off-white to yellowish-tan with iron staining. Luster: dull to vitreous. Crystal structure: trigonal (microcrystalline). Texture: grainy, non-foliated, water-worn. Specific gravity: 2.63-2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic. This specific specimen has been further shaped by fluvial or glacial erosion into a rounded pebble.
Uses & applications
Informally used as a decorative stone, in construction as crushed aggregate, and for historical tool-making. High-purity quartzite is used in glassmaking and electronics.
Geological facts
Quartzite is so durable that it can survive long-distance transport in rivers and glacial paths. It is often harder than the steel knives used to test it.
Field identification & locations
Identify by its inability to be scratched by steel and its grainy, sugary look under a lens. Found worldwide in riverbeds, beaches, and glacial till. Common in areas with ancient mountain belts.
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