sedimentary
Chert (specifically Flint or Jasper variant)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Brown, tan, cream, and beige banding; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (has Choncoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Brown, tan, cream, and beige banding
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Brown, tan, cream, and beige banding; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (has Choncoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or chemical precipitation from groundwater within limestone or chalk beds. Often found in nodules within sedimentary basins.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Modern uses include construction aggregates, road surfacing, and decorative landscaping stones.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges. This specific banded pattern is common in specimens found in glacial till or river gravels.
Field identification & locations
Identify by its 'sharp' shell-like fracture surfaces and ability to scratch glass easily. It is found globally in sedimentary environments, river beds, and coastal areas.
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