OMG, that looks like quite a load for a truss-rod flat car with arch bar trucks!
This is just the kind of info I was hoping for. Some covered (finished, I guess) stones and some not covered, and how they are fastened.
I am thinking about including a finishing plant down on the mainline, not far from where the quarry branch comes in. So, blocks would probably go there uncovered from the quarry, but might go out from there with covers. I am thinking that covers would really only serve to keep the coal grime off the light colored rock. In my location (Allegheney Plateau) and era (transition period), only sandstone seems like a credible dimensional rock product. And, sandstone is more easily stained than granite, hence covers seem logical.
Thanks for the info. More on quarrying or finishing would still be appreciated.