Rick:
Thanks for the information...
The D&RGW applied to the ICC to abandon the Blue River branch on September 15, 1923. Approval was granted in 1924 and the rails were removed that summer. The D&RGW applied to abandon the Calumet branch from Hecla Junction to Calumet at the same time. I think the C&S took over a D&RG spur in Kokomo to the smelter. A D&RGW retired agent told me that C&S narrow gauge cars were still bringing in anthracite coal from the Crested Butte branch as late as 1923 and 24.
I simply speculated that C-16 number 216 might have been used on the Blue River or Ibex branches. Apparently it was used out of Durango on the RGS. The D&RGW had C16s in Leadville as late as 1925, so anything was possible.
I have spoken with retired D&RGW engineers who worked on both the Baldwin and Pitkin branches (you were correct that it went to Quartz). The mixed train only ran as far as Pitkin, but the engine would run up to Quartz when necessary. The same type of operation was typical on the Baldwin branch. The mixed ran as far as Castleton with the engine switching the mines at Baldwin and Kubler while the passenger car waited at the depot in Castleton.
Jerry