Ghost Rock is a mineral discovered in the wake of the Great Quake of 1868, first in California, and then in other locations (particularly in the Black Hills of Dakota (now the Sioux Nation). It is dark gray in color, mottled with whitish flecks. It burns a hundred times hotter and longer than coal, and even burns (for a short time) under water. It has been employed largely in engineering and military applications, but its utility extends to virtually all areas of society in the Weird West.
Notably, when burned, ghost rock also screams. It is chiefly this which led to its name: legend has it that the rock contains souls of the damned. Scientists of course, scoff at such ideas and point to the fact that ghost rock contains tiny air pockets, and these are responsible for the fact that the mineral burns under water, and for the sound it makes.
Nevertheless, those who work with ghost rock for long periods of time tend to suffer mental instability, and it does tend to show up in places where it is likely to provoke unrest and conflict. The largest known sources of ghost rock are the Great Maze in California and the Black Hills in the Sioux Nation.