sedimentary
Chert (Jasper/Agate variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, gray, and blue-green; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Reddish-brown, gray, and blue-green
- Luster
- Vitreous to waxy
Identified More sedimentary →
Explore Chert (Jasper/Agate variety) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, gray, and blue-green; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich fluids in limestone or volcanic rock cavities. Often occurs as nodules or replacement deposits. Geological age varies greatly from Precambrian to Cenozoic.
Uses & applications
Used historically for stone tools and weapons due to its sharp edges; modern uses include lapidary work, jewelry, and landscaping. High-quality specimens are popular among rockhounds.
Geological facts
This specimen shows transitions between opaque jasper and translucent chalcedony. Historically, chert was a primary material for making arrowheads and spear points because of its predictable fracturing patterns.
Field identification & locations
Identify by its 'shell-like' shell-like (conchoidal) fracture and its ability to scratch glass. Commonly found in stream beds, gravel pits, and sedimentary rock outcrops. Collectors should look for unique banding or color inclusions.
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