metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to yellowish-brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); 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 in orogenic belts. This specific specimen is a water-worn river pebble, likely shaped during the Quaternary period.
Uses & applications
Used as aggregate in construction, railway ballast, and occasionally for lapidary tumbling or as decorative garden stone.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, ending up as resilient pebbles in riverbeds. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify in the field by its sugary texture on broken surfaces and its extreme hardness. Common in riverbeds, glacial tills, and mountainous regions worldwide.
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