metamorphic
Quartzite Pebble
Metamorphic Quartz Sandstone (SiO2)
Hardness: 7 on the Mohs scale; Color: Grayish-white with darker mottle and yellowish weathering; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None, fractures conchoidally; Specific gravity: 2.65
- Hardness
- 7 on the Mohs scale
- Color
- Grayish-white with darker mottle and yellowish weathering
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale; Color: Grayish-white with darker mottle and yellowish weathering; Luster: Vitreous to greasy; Crystal structure: Trigonal (microcrystalline quartz grains fused together); Cleavage: None, fractures conchoidally; Specific gravity: 2.65
Formation & geological history
Formed from quartz-rich sandstone subjected to intense heat and pressure during regional metamorphism, fusing the quartz grains together into a hard, solid mass. Geological age varies widely depending on location, ranging from Precambrian to Cenozoic.
Uses & applications
Used in construction, as a decorative stone, in road aggregate, and for manufacturing silica brick and ferrosilicon.
Geological facts
Quartzite is extremely resistant to weathering and erosion, which is why it frequently survives long journeys in riverbeds or ocean waves to become smooth, rounded pebbles found on beaches.
Field identification & locations
Can be identified in the field by its hard vitreous surface that cannot be scratched by a steel knife and the way it breaks across the quartz grains rather than around them. Common worldwide in coastal beaches, river gravels, and ancient mountain belts.
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