sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs); Color: Tan, beige, or grey with waxy/dull luster; Crystal Structure: Microcrystalline quartz; Conchoidal fracture (breaks like glass); Specific gravity: 2.65.
- Hardness
- 7 (Mohs)
- Color
- Tan, beige, or grey with waxy/dull luster
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Physical properties
Hardness: 7 (Mohs); Color: Tan, beige, or grey with waxy/dull luster; Crystal Structure: Microcrystalline quartz; Conchoidal fracture (breaks like glass); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich marine micro-organisms or chemical precipitation within limestone/chalk beds during the Paleozoic or Mesozoic eras.
Uses & applications
Historically used for stone tools and starting fires; currently used in road construction, landscape gravel, and sometimes as a flux in glassmaking.
Geological facts
Chert is so hard it can scratch steel. When struck against steel, it produces sparks, making it a primary material for flintlock firearms and ancient survival fire-starting.
Field identification & locations
Identify by its 'waxy' texture and sharp, shell-like (conchoidal) breaking pattern. Frequently found in stream beds or weathered out of limestone cliffs.
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