sedimentary
Chert (Red Jasper variant)
Silicon dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Brick red to brownish-red; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brick red to brownish-red
- Luster
- Dull to waxy
Identified More sedimentary →
Explore Chert (Red Jasper variant) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Brick red to brownish-red; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or volcanic environments, later lithified into dense rock. Often found in nodules within limestone or as bedded deposits.
Uses & applications
Historically used for stone tools (knapping); currently used for jewelry, lapidary cabochons, landscaping, and industrial abrasives.
Geological facts
Red chert is often called Jasper when it is opaque and colored by iron inclusions. It has been used by humans for hundreds of thousands of years to create sharp-edged tools due to its predictable conchoidal fracturing.
Field identification & locations
Identify in the field by its high hardness (scratches glass), smooth waxy feel, and characteristic shell-like (conchoidal) curved breakage patterns. Commonly found in river beds or eroded sedimentary outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary