metamorphic
Quartzite (Beach Pebble)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Creamy white to pale tan/yellow; Luster: Vitreous to waxy after water rounding; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7.
- Hardness
- 7 on Mohs scale
- Color
- Creamy white to pale tan/yellow
- Luster
- Vitreous to waxy after water rounding
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Physical properties
Hardness: 7 on Mohs scale; Color: Creamy white to pale tan/yellow; Luster: Vitreous to waxy after water rounding; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. This specimen has been significantly rounded and smoothed by wave action in a beach environment.
Uses & applications
Used industrially as a source of silica, in construction as crushed stone or road ballast, and in landscaping. Polished beach pebbles are popular in home decor and zen gardens.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it was formed in. When struck with a hammer, quartzite will break through the quartz grains rather than around them, unlike its parent stone, sandstone.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and lack of visible grains compared to sandstone. Commonly found on beaches near glaciated coastlines or mountain runoff areas. Collectors look for unique smooth shapes and translucency.
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