sedimentary
Chert (Yellow Jasper/Quartzite Pebble)
Microcrystalline Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: tan to honey-yellow, Luster: waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: tan to honey-yellow, Luster: waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians) or chemical precipitation from groundwater. This specific specimen appears to be water-worn, smoothed by alluvial or marine transport over millions of years.
Uses & applications
Used primarily in landscaping, road construction (as gravel), and historically as a material for stone tools (lithics) due to its sharp edges when broken.
Geological facts
Because of its high hardness and lack of cleavage, this material was used by prehistoric humans to create arrowheads and scrapers. It can produce sparks when struck against steel.
Field identification & locations
Identify in the field by its hardness (it should scratch glass), waxy feel, and smoothed, rounded outer surface. It is commonly found in riverbeds, along beaches, and within sedimentary conglomerate layers.
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