sedimentary
Chert (Arrowhead variety)
Chert (SiO2)
AI-generated identification · may be incorrectHardness: 6.5 - 7 (Mohs scale); Color: Dark brown to black (flint-like); Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7.
- Hardness
- 6
- Color
- Dark brown to black (flint-like)
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5 - 7 (Mohs scale); Color: Dark brown to black (flint-like); Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by the chemical replacement of limestone/dolomite. It is common in Phanerozoic sedimentary sequences.
Uses & applications
Historically used for stone tools and weapons due to its ability to hold a sharp edge. Industrially used as an abrasive or in construction aggregate. Highly valued by archaeological collectors.
Geological facts
This specimen is a 'projectile point,' an artifact crafted through a process called knapping. Chert was the 'steel of the ancient world' because its conchoidal fracture creates edges sharper than a modern steel scalpel.
Field identification & locations
Identify in the field by looking for 'scalloped' or shell-like fracture patterns (conchoidal) and a waxy texture. Often found as nodules within limestone outcrops or as weathered pebbles in stream beds.
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