sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2) with hematite impurities
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, tan, and cream mottled; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
- Hardness
- 6
- Color
- Reddish-brown, tan, and cream mottled
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, tan, and cream mottled; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. Often found as nodules in limestone or as bedded deposits.
Uses & applications
Used historically for stone tools and weapons due to its sharp edges; currently used for lapidary work, jewelry (tumbled stones), and as a landscape rock.
Geological facts
Red chert is often called Jasper. It was one of the first materials used by early humans to create flaked tools because it breaks with a predictable, sharp conchoidal fracture.
Field identification & locations
Identified in the field by its hardness (scratches glass), waxy feel when smooth, and sharp, shell-like fracture patterns. Common in gravel beds and sedimentary outcrops worldwide.
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