sedimentary
Chert Pebble
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Gray, beige, and dark charcoal banded; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6
- Hardness
- 7 (Mohs scale)
- Color
- Gray, beige, and dark charcoal banded
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Gray, beige, and dark charcoal banded; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6
Formation & geological history
Formed via the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments; this specimen shows water-worn rounding from river or beach transport.
Uses & applications
Historically used for stone tools and fire-starting; currently used for decorative gravel, landscaping, and as a common find for beachcombers.
Geological facts
Chert is so durable that it can survive millions of years of erosion. Variants include flint (dark) and jasper (red). It was one of the most important raw materials for prehistoric humans.
Field identification & locations
Identify by its extreme hardness (scratches glass), waxy feel, and smooth, rounded water-worn shape. Commonly found on beaches, riverbeds, and in limestone outcrops worldwide.
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