sedimentary
Banded Chert
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, and dark grey banding; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brown, tan, and dark grey banding
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, and dark grey banding; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. The banding represents changes in sediment supply or oxygen levels over millions of years.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used in landscaping, as an abrasive, and by rock hounds for lapidary work.
Geological facts
Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, similar to its close relative, flint.
Field identification & locations
Identify by its horizontal layering (banding), smooth waxy feel when wet, and sharp edges when broken. Frequently found in riverbeds or within limestone and dolostone formations.
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