We're all wrong. Here's some more info on that compressor. Looks like it was powered by electricity. There's a video on youtube of what I think is one....although it doesn't specify. Looks like the same type armature and says 750HP and 2300V. But here's an article about them. Clearly this one is electric. What appears like a steam engine is the compressor pump. lol
According to the signs around there, it powered the mill and the tramway to get the gold ore down to the mill. I didn't see any evidence of a boiler but that don't mean anything. I was impressed they could get that thing 13
thousand feet up the side of a mountain.