I was hunting that area in the mid 60s. They were surely there. Just exactly what they were doing, is still a mystery to me.
Found an Arrastre in western Mason, Co., that the stones were flat, but stacked "vertically" in the circle. The dia was 4'.
Not far way was a red hill, which I didnt realize till after leaving the area. This "hill" is on private property, and is as red as the "Red Chispa" mine, in CA. Not far away was more hematite,magnasite than Ive ever seen!
have a "little" more, but access would be hairy.
HOGE