sedimentary
Chert (Pink/Red variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on the Mohs scale. Color: Salmon pink to dull red (iron-stained). Luster: Waxy to dull. Crystal Structure: Hexagonal (microscopic). Cleavage: None, exhibits sharp conchoidal (shell-like) fracture. Specific Gravity: 2.65.
- Hardness
- 7 on the Mohs scale
- Color
- Salmon pink to dull red (iron-stained)
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on the Mohs scale. Color: Salmon pink to dull red (iron-stained). Luster: Waxy to dull. Crystal Structure: Hexagonal (microscopic). Cleavage: None, exhibits sharp conchoidal (shell-like) fracture. Specific Gravity: 2.65.
Formation & geological history
Formed through the precipitation of silica from groundwater or the accumulation of silica-rich biogenic remains (like radiolarians) on the seafloor. It often replaces original carbonate materials in limestone. Most common specimens vary from Precambrian to Cenozoic in age.
Uses & applications
Historically used by indigenous peoples for stone tools, arrowheads, and fire-starting. Currently used as an abrasive, in road construction (aggregate), and for lapidary work (polishing for jewelry or display).
Geological facts
Because of its high hardness and brittle nature, it produces razor-sharp edges when broken, which is why it was the primary material for prehistoric weaponry. Some red varieties are specifically referred to as jasper.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sharp, curved edges where broken. It is commonly found as nodules within limestone formations or as extensive 'bedded chert' layers in sedimentary basins.
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