A large <a href="https://en.wikipedia.org/wiki/Marcasite" class="extiw" title="en:Marcasite">Marcasite</a> crystal from the <a rel="nofollow" class="external text" href="http://www.eos.ubc.ca/resources/museum/history.html">Pacific Museum of the Earth</a>.
<a href="//commons.wikimedia.org/wiki/User:The_High_Fin_Sperm_Whale" title="User:The High Fin Sperm Whale">The High Fin Sperm Whale</a>
CC BY-SA 3.0
<span class="int-own-work">Self-photographed</span>