sedimentary
Chert (Jasper/Chalcedony variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: honey-yellow, orange-brown, and tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none, exhibits conchoidal fracture; Specific gravity: 2.6-2.65
- Hardness
- 6
- Color
- honey-yellow, orange-brown, and tan
- Luster
- waxy to vitreous
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: honey-yellow, orange-brown, and tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none, exhibits conchoidal fracture; Specific gravity: 2.6-2.65
Formation & geological history
Formed through the accumulation of silica-rich fluids in sedimentary basins or by the replacement of limestone. This specimen likely formed during the Cenozoic or Mesozoic eras through chemical precipitation.
Uses & applications
Historically used for stone tools (knapping); currently used for lapidary work, jewelry (cabochons), and as a decorative landscaping rock.
Geological facts
Because of its high hardness and conchoidal fracture, this material was one of the most important resources for prehistoric humans to create sharp-edged arrowheads and knives.
Field identification & locations
Identify by its 'waxy' appearance, hardness (it will scratch glass), and the shell-like (conchoidal) curves where it has chipped. Commonly found in riverbeds, desert pavements, and limestone outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary