sedimentary
Chert (Jaspery variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, beige, and grayish-white. Luster: Waxy to dull. Structure: Cryptocrystalline/Microcrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 6
- Color
- Tan, beige, and grayish-white
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, beige, and grayish-white. Luster: Waxy to dull. Structure: Cryptocrystalline/Microcrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers, often limestone or chalk. Commonly found in ancient marine environments.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to sharp edges; currently used in construction aggregate and as a semi-precious stone for lapidary work.
Geological facts
Chert was one of the most important minerals for early humans because of its ability to fracture with extremely sharp, glass-like edges. It is chemically identical to quartz but contains impurities.
Field identification & locations
Identify by its hardness (will scratch glass), smooth waxy feel on broken surfaces, and distinct conchoidal (shell-like) fracture patterns. Frequently found in stream beds and road cuts.
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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