Carboniferous Chert found in Lancashire supplied in a card tray with label.
Chert is a very hard, fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color from white to black, but most often it is grey, brown, red or greenish. It can occur as a primary deposit or as a replacement mineral during diagenesis e.g. Flint nodules in Chalk. This example is from the Carboniferous deposits of Lancashire, U.K. Specimens are supplied in labelled card trays.