According to a website, the Mojave Northern opened around 1916 by Southwestern Portland Cement to move limestone 6 miles from Sidewinder Valley to Victorville. Just after World War II, the line was extended another 7 miles to Bell and then another 7 miles to Reserve Quarry in 1951.
Lots of photos of the Railway Club of Southern California excursion on the Mojave Northern can be seen here:
The July 1981 Trains magazine had an article about the club's excursions which possibly had a photo of the trip.
The Pacific Railroad Society excursion that ran shortly after a branch to a cement plant was constructed was the one on the Cushenberry Branch on May 19, 1957.