metamorphic
Quartzite River Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Creamy white to light tan; Luster: Dull/waxy when unpolished, vitreous when broken; Crystal Structure: Granular/Massive (Microcrystalline); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Creamy white to light tan
- Luster
- Dull/waxy when unpolished, vitreous when broken
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Physical properties
Hardness: 7 on Mohs scale; Color: Creamy white to light tan; Luster: Dull/waxy when unpolished, vitreous when broken; Crystal Structure: Granular/Massive (Microcrystalline); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from quartz-rich sandstone subjected to intense heat and pressure (metamorphism). The rounded 'kidney' shape is a result of fluvial erosion in a river or coastal environment over thousands of years.
Uses & applications
Decorative landscaping, building material, aggregate for concrete, and occasionally used in water filtration or as a pocket stone/talisman.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers during erosion. This specific 'kidney' or 'comma' shape is a classic example of mechanical weathering in high-energy water environments.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its smooth, rounded surface. Found globally in riverbeds and on beaches. Collectors look for unique ergonomic shapes.
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