Aluminium oxide skimmed off the surface of molten aluminium.
<a href="//commons.wikimedia.org/w/index.php?title=User:Nbritton&amp;action=edit&amp;redlink=1" class="new" title="User:Nbritton (page does not exist)">Nbritton</a>
2008
<span class="int-own-work" lang="en">Own work</span>