Coal ball: Difference between revisions

|image_caption=A coal ball

|composition=Permineralised plant remains

 

A '''coal ball''' is a type of [[concretion]], varying in shape from an imperfect sphere to a flat-lying, irregular slab. Coal balls were formed in [[Carboniferous|Carboniferous Period]] swamps and mires, when [[peat]] was prevented from being [[wikt:coalification|turned into coal]] by the high amount of [[calcite]] surrounding the peat; the calcite caused it to be [[permineralisation|turned into stone]] instead. As such, despite not actually being made of [[coal]], the coal ball owes its name to its similar origins as well as its similar shape with actual coal.