This Rock oil candle / Rock oil lamp is built around a fish fossil from Wyoming.
Huge lakes covered parts of Southwest Wyoming about 50 million years ago during what is known as the Eocene period. Fine grained sediments collected at the bottom of these lakes that preserved the fossils of millions of fish. Over time, these sediments turned to stone resulting in the fish fossil.
The fossil fish found in the rock candle are known as Knightia, a herring-like, schooling fish. They averaged about 3-4 inches in length, but have also been found up to 10 inches long. Similar to modern freshwater fish, Knightia had four fins, ones on its back, stomach, pelvis, and anus. It is figured that they likely ate plankton and algae and was a food source for many of the larger fish of the time.
The Knightia fish fossil is a actually the state fossil of Wyoming.