metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: Creamy white to pale yellow. Luster: Vitreous to dull. Crystal structure: Non-foliated, granular. Cleavage: Indistinct/none. Specific gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Color
- Creamy white to pale yellow
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Creamy white to pale yellow. Luster: Vitreous to dull. Crystal structure: Non-foliated, granular. Cleavage: Indistinct/none. Specific gravity: ~2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize and fuse together into a dense, hard rock. Typically associated with mountain-building events.
Uses & applications
Used as a construction aggregate, in road metal, as a decorative stone in landscaping, and sometimes as a source of silica for glass manufacturing.
Geological facts
Quartzite is so hard and dense that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent rock, sandstone.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, crystalline surface. Common in river beds, beaches, and glaciated areas as smoothed pebbles.
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