<p>Photographer: <a href="//commons.wikimedia.org/wiki/User:Siim" title="User:Siim">Siim Sepp</a>
Date of the creation: 20th April, 2005.
</p>
Kukersite is shale oil from Estonia, Ordovician system.
No machine-readable author provided. <a href="//commons.wikimedia.org/wiki/User:Siim" title="User:Siim">Siim</a> assumed (based on copyright claims).
CC BY-SA 3.0
No machine-readable source provided. Own work assumed (based on copyright claims).