sedimentary
Chert (Jasper variation)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Brownish-red to chocolate brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Brownish-red to chocolate brown
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Jasper variation) 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: Brownish-red to chocolate brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed via the accumulation of silica-rich microfossils or chemical precipitation of silica in marine environments, subsequently hardening over millions of years. This specimen shows significant tumbling/rounding, likely from river or beach action.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for lapidary work, landscaping, and gemstone collecting.
Geological facts
Chert is so durable that it can survive long periods of environmental transport. The specific brown/red colors are usually caused by inclusions of iron oxides.
Field identification & locations
Identified by its extreme hardness (will scratch glass), waxy luster, and conchoidal (shell-like) fracture patterns. Often found in gravel beds or eroded out of limestone formations.
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
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary