metamorphic
Quartzite Beach Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or off-white; Luster: Vitreous to dull; Crystal structure: Non-foliated/Granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or off-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or off-white; Luster: Vitreous to dull; Crystal structure: Non-foliated/Granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped by fluvial or coastal erosion, gaining its rounded, smooth texture from constant tumbling by sea waves.
Uses & applications
Used as decorative landscaping stone, in construction aggregates, and occasionally as a source of silica for glassmaking. Smooth beach pebbles are popular for meditation stones, craft projects, and aquarium décor.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges from which it originated. It is harder than steel and will easily scratch glass. This rounded shape, known as high sphericity, indicates a long journey from its original source rock.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife) and its grainy, crystalline texture that looks like fused sugar. Common on beaches near mountain ranges with tectonic history. Helpful for collectors to practice identifying metamorphic vs. sedimentary stones.
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