Pyrite

Field of view: 5 mm. Scepter crystals of pyrite. The dark gray cubes are pyrite. The center of each face is hollow. This crystal form is called a scepter crystal. Scepter crystals were formed by rapid growth of edges and corners. Edges and corners grows faster when the growth rate-determining process is material supply because protruded edges and corners consume materials. The earthy dark gray parts on the crystals are the host mudstone.

Recovered from mudstone deposited in a deep submarine environment.