sedimentary
Chert (White Variety)
Microcrystalline Silica (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Cream to white; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6
- Hardness
- 6
- Color
- Cream to white
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Cream to white; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6
Formation & geological history
Formed as nodules or layers in limestone through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation from groundwater.
Uses & applications
Historically used for stone tools and arrowheads due to sharp edges; currently used for landscaping, road ballast, and concrete aggregate.
Geological facts
Chert is chemically identical to quartz but has a much finer grain structure. High-quality varieties of chert are often called flint. It is one of the most common materials used by early humans for lithic technology.
Field identification & locations
Identify by its waxy luster, extreme hardness (scratches glass), and shell-like (conchoidal) fracture pattern. Commonly found in stream beds or within limestone outcrops.
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Brecciated Chert (Microcrystalline Silica)
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