sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 6.5 - 7 on the Mohs scale. Color: Mottled brown, tan, and gray with waxy luster. Crystal structure: Cryptocrystalline (microscopic quartz). Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.7.
- Hardness
- 6
- Color
- Mottled brown, tan, and gray with waxy luster
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Physical properties
Hardness: 6.5 - 7 on the Mohs scale. Color: Mottled brown, tan, and gray with waxy luster. Crystal structure: Cryptocrystalline (microscopic quartz). Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.7.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen likely originates from Paleozoic or Mesozoic sedimentary beds.
Uses & applications
Historically used for stone tools (knapping). Currently used as an abrasive, in landscaping/construction, and as lapidary material for jewelry like cabochons.
Geological facts
Due to its conchoidal fracture, it breaks with sharp, curved edges similar to glass, which made it the primary material for arrowheads and scrapers for prehistoric humans.
Field identification & locations
Identify in the field by its smooth, shell-like fracture pattern and high hardness (it will scratch steel and glass). Commonly found in limestone or chalk deposits as nodules or layers.
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