metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, off-white, or light gray; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, off-white, or light gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, off-white, or light gray; Luster: Vitreous to dull; Crystal structure: Trigonal/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 during mountain-building events. This specimen has been rounded by fluvial (river) or coastal water erosion.
Uses & applications
Used as a decorative landscape stone, in construction aggregates, or as a source of silica in glassmaking. Small river-worn pebbles are often used in ornamental gardens or aquariums.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it helped form. When it breaks, unlike sandstone which breaks around sand grains, quartzite breaks through the grains due to the complete recrystallization of the silica.
Field identification & locations
Identify by its ability to scratch glass and its grainy but fused texture. It is extremely common in riverbeds and glacial deposits worldwide. Collectors look for unique banding or translucency.
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