![](https://www.ciphercoal.com/wp-content/uploads/2016/10/Tim-2-300x200.jpg)
The lyrics of Neil Young* were going through my head as we trundled down the decline of a mineshaft at 3000 m elevation. We had left the brilliant blue skies of the Andean cordillera moments before, plunging into the darkened tunnel; we were headed for the Guaduas Formation (Late Cretaceous – Paleocene), which contains some […]