metamorphic
Quartzite pebble
Quartzite (SiO2 with iron oxide staining)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Yellowish-brown to tan due to limonite/iron oxide staining; Luster: Dull to vitreous; Structure: Granoblastic interlocking quartz grains; Cleavage: None; Specific Gravity: ~2.65
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-brown to tan due to limonite/iron oxide staining
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-brown to tan due to limonite/iron oxide staining; Luster: Dull to vitreous; Structure: Granoblastic interlocking quartz grains; Cleavage: None; Specific Gravity: ~2.65
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism. The original sand grains recrystallize into a dense, hard mosaic of interlocking quartz crystals. Later rounded and weathered by beach wave action and stained by iron-rich water.
Uses & applications
Beach pebbles like this are used in decorative landscaping, aquariums, pebble mosaics, and craft projects. High-purity quartzite is crushed for industrial silica glass and silicon metal production.
Geological facts
Quartzite is extremely resistant to chemical weathering and erosion. When broken, quartzite fractures through the quartz grains rather than along grain boundaries like sandstone.
Field identification & locations
Can be identified by its extreme hardness (scratches glass easily), sugary/granular texture under magnification, rounded beach-worn shape, and yellowish iron oxidation staining. Commonly found along coasts, rivers, and glacial till worldwide.
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