First, and foremost it was the discovery of gold at the base of Diamond Mountain in 1855/56 that was impetus to bring Anglo settlers into the Honey Lake Valley. This was placer mining, gold found of stream beds. However, this source of gold quickly panned out (pun intended). The other is lode mining, i.e. hard rock via tunnels.

As to inquirer, in regards to the Union Mine, George McDow, Jr. wrote Mining-Diamond Mountain that was published in April 1965, Bulletin No. 13 of the Lassen County Historical Society. In 1939/40 this mine was featured in the California Division Mines Bulletin. Unfortunately, for the latter, while I possess a copy of the same, I am unable to provide specific details of that publication due to chaos of my recent move.

It has been relayed to me, that Diamond Mountain present challenges with hard rock mines, since the mountain is a fault block. One can hit a rich vein of gold, then it suddenly disappears. The question is did fault move the vein up or down?

Tim