Chert (/ˈtʃɜːrt/) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide...

is made up of three formations, the Grassy Knob Chert, the Backbone Limestone and Clear Creek Chert. It is Lower Devonian in age. Eastward the group...

microorganisms permineralized in 3.465-billion-year-old Australian Apex chert rocks. However, the evidence for the biogenicity of these microstructures...

57°20′12″N 002°50′29″W / 57.33667°N 2.84139°W / 57.33667; -2.84139 The Rhynie chert is a Lower Devonian sedimentary deposit exhibiting extraordinary fossil...

The Huntersville Chert or Huntersville Formation is a Devonian geologic formation in the Appalachian region of the United States. It is primarily composed...

white chert. Facies 3, which overlies facies 2, consists largely of centimeter-layered chert. The layered chert consists of white-gray layered chert and...

The Bigfork Chert is a Middle to Late Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892, this...

and William H. Lang in 1917. The species is known only from the Rhynie chert in Aberdeenshire, Scotland, where it grew in the vicinity of a silica-rich...

Clifty Limestone is very sandy, light blue to bluish grey. The Penters Chert is a Devonian geologic formation in the Ozark Plateaus of Arkansas. Its...

The Princeton Chert is a fossil locality in British Columbia, Canada, which comprises an anatomically preserved flora of Eocene Epoch age, with rich species...