It releases an electrical charge while 'breathing' iron minerals, experiments showed.

They normally contain fossil debris and sometimes the fossils are partly or entirely replaced by iron minerals.

There are also numerous excavations that included iron minerals.

The most reactive of the iron minerals are the iron sulfides and oxides.

The nodules consist of iron minerals, carbon substances and mica; as the metamorphic temperature rises, minerals such as andalusite or chiastolite increasingly occur.