sedimentary
Chert (Flint)
Silicon dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 on Mohs scale; Color: white, gray, orange, or brown; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 6
- Color
- white, gray, orange, or brown
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: white, gray, orange, or brown; Luster: waxy to dull; Structure: microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or by the chemical precipitation of silica in groundwater within limestone or chalk beds. Often dated from the Paleozoic to Mesozoic eras.
Uses & applications
Historically used for stone tools and weapons (arrowheads); currently used as a raw material for road construction, in ceramics, and as a landscaping stone.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, ideal for cutting and skinning.
Field identification & locations
Identify in the field by its waxy appearance and the shell-like (conchoidal) curves where it has broken. Commonly found in riverbeds or as nodules within limestone outcrops.
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