According to Wikipedia, "Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite."
Apparently you can get oil out of stone! One of the interesting walks you can do from a Newnes camping ground is the Newnes Industriall Ruins site. It was the site of one of the largest shale oil production schemes in Australia and operated between 1906 and 1932.
These are coke ovens. The only 'coke' I knew was the one which I drink, but this is not that Coke. These coke ovens were used to fuel the boiler plants.
Once you get past the uphill bit, the walk is pretty easy and interesting. It has an 'Indiana Jones' feeling to it as you see crumbling brick and nature re-conquering what was once its domain. You can picture in your mind's eye the hive of activity that once filled the place and contrast that with the utter stillness of today.
The other walk we did was the Glow Worm Tunnel. That was very interesting, though you had to work for that one.