metamorphic

Quartzite River Pebble

Metamorphosed Quartz Sandstone (SiO2)

AI-generated identification · may be incorrect

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

Identified May 21, 2026More metamorphic →

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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.