This branch extended west from Union Pacific's mainline at Arden (south of Las Vegas) and extended to a gypsum plant near Blue Diamond. At some point, most likely in the 1980s, this line was abandoned, and the gypsum plant started using trucks for their shipments.
The far eastern segment is still in place, and appears to be used for car storage. The center segment has been partially obliterated by new housing developments. The far western segment, near the gypsum plant, traveled on remote private property.
Thanks to Mike Palmer for contributing information about this route.