sedimentary
Chert (Yellow Jasper variant)
Microcrystalline Quartz (SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Opaque yellow to tan. Luster: Waxy to dull. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: Approximately 2.6.
- Hardness
- 6
- Color
- Opaque yellow to tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Opaque yellow to tan. Luster: Waxy to dull. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: Approximately 2.6.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds. Formation can span from the Precambrian to recent eras.
Uses & applications
Historically used for stone tools/arrowheads. Currently used in jewelry (cabochons), as decorative landscaping stone, and in concrete aggregate.
Geological facts
Chert was one of the most vital materials for early humans because its conchoidal fracture produces razor-sharp edges. When struck against iron pyrites or steel, it can produce sparks to start fires.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its waxy texture, and its smooth, shell-like (conchoidal) kırılma or breakage pattern. Commonly found in riverbeds or eroded limestone outcrops.
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