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Pea Grit (pisolite) is the name given to a Middle Jurassic limestone which is characterised by its large spherical grains or Pisoids, similar to ooliths. Specimens are supplied with a labelled card tray.
A pisolite is a sedimentary rock made of pisoids, which are concretionary grains – often of calcium carbonate, but sometimes of rarer minerals – which resemble ooids but are always more than 2 mm in diameter. These grains are approximately spherical and have concentric layers which can reach reach 10 mm in diameter. It's formation is similar to that of an oolite. This example is known as the Pea Grit from the Crickley Hill member of the Middle Jurassic (Aalenian, 177 -180ma) from Gloucestershire. It is fossiliferous, containing abundant bivalves, echinoids , brachiopods & corals. Specimens are supplied in labelled card trays.