Because the fern leaves were rapidly buried by the sediment deposited in the deltaic system, they have retained their leaf structure. Bacterial decomposition of the remains produced carbon dioxide that combined with dissolved iron from the groundwater. This process formed siderite in the sediments surrounding the remains, forming detailed casts of their structure. Lithification of the sediments formed protective nodules of ironstone around the now fossilized remains. The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas. Once found in ample quantities, the concretions are now more difficult to locate.
Energetically, these are very useful natural healing tools. There is a positive and a negative side which is excellent to place around an injury spot (such as an arm or finger) or an impacted energy spot to clear the energy and get it flowing again.