sedimentary
Chert (Jasper variation)
Chert (Silicate mineral, SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Rusty orange/brown, Luster: Waxy to dull, Crystal structure: Microcrystalline (Trigonal), Cleavage: None (conchoïdal fracture), Specific gravity: 2.6-2.7
- Hardness
- 6
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Rusty orange/brown, Luster: Waxy to dull, Crystal structure: Microcrystalline (Trigonal), Cleavage: None (conchoïdal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation in saltwater environments. It commonly forms as nodules or bedded deposits throughout various geological ages.
Uses & applications
Historically used for stone tools (knapping) due to its sharp edges. Currently used for lapidary work, jewelry (especially as beads or cabochons), and as a landscaping stone.
Geological facts
Chert was one of the most important raw materials for early humans to create arrowheads and scrapers. The orange-brown variety shown is often colloquially called Jasper when it contains significant iron oxide impurities.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its curved, shell-like (conchoidal) fracture pattern when broken. Commonly found in riverbeds or within limestone formations worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary