sedimentary
Chert (Jasper / Flint variant)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, yellowish-brown, brownish-red with distinct iron oxide banding. Luster: Waxy to dull/earthy. Crystal Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (features smooth conchoidal to sub-conchoidal fracture). Specific Gravity: 2.58 - 2.64.
- Hardness
- 7 on Mohs scale
- Luster
- Waxy to dull/earthy
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, yellowish-brown, brownish-red with distinct iron oxide banding. Luster: Waxy to dull/earthy. Crystal Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (features smooth conchoidal to sub-conchoidal fracture). Specific Gravity: 2.58 - 2.64.
Formation & geological history
Formed via chemical precipitation of silica-rich fluids or biological diagenesis of silica-rich ooze (such as radiolarians or diatoms) in marine or freshwater environments. Secondary iron oxides create the distinctive reddish-brown banding.
Uses & applications
Historically used for making stone tools, arrowheads, and flintlock strikers due to its sharp conchoidal edges. Currently used in lapidary work, cabochon crafting, decorative landscaping, and stone collecting.
Geological facts
Chert and jasper have been used by humans for hundreds of thousands of years for toolmaking. When struck with steel or iron pyrite, chert generates sparks, making it one of humanity's earliest fire-starting materials.
Field identification & locations
Identified in the field by its hardness (scratches glass readily), smooth waxy feel, sharp edges on broken surfaces, and distinct color banding. Commonly found in limestone formations, stream beds, and gravel deposits worldwide.
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