sedimentary
Chert (often called Flint or Jasper)
Microcrystalline or cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and reddish-orange due to iron oxides. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Brown, tan, and reddish-orange due to iron oxides
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and reddish-orange due to iron oxides. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of siliceous remains of organisms or chemical precipitation. This specific sample shows banding indicative of varying mineral impurity deposition in a sedimentary environment.
Uses & applications
Historically used for stone tools (knapping) due to its sharp edges; currently used for road surfacing, lapidary work, and landscaping.
Geological facts
Chert was one of the most vital materials for early humans because its conchoidal fracture allows it to be shaped into razor-sharp arrowheads and knives.
Field identification & locations
Identify in the field by its smooth, waxy texture and curved, shell-like (conchoidal) fracture patterns when broken. Commonly found in limestone and chalk deposits.
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