The vertically drilled hole was created with a machine called a "raise-borer". That's why the sides look relatively smooth. It would have eventually been, with further work, turned into a "ore pass." Blasted rock would then be dropped down into the ore pass, breaking into smaller pieces on the way down. At the bottom of the ore pass would be a large metal grate, which could be opened to allow ore to be transported by rail cars or a front-end loaders. This ore pass would have been about 1,500 feet deep.
In the case of this particular mine, the ore would have been transported by rail to the portal, and then moved to the Pine Mine crusher system for further processing.
When the price of tungsten collapsed, the company decided not to proceed with further operations in the Brown Stone mine.
I should probably have a chat with the experienced, retired miners who still work at Pine Creek, to get their opinion of the condition of the interior of the Brown Stone mine, before venturing into possible danger. Better safe than sorry, eh?. Remember what was said about space travel: "In the silence of space, no one can hear you scream." Same applies to underground mines.
Have you ever considered studying for a mine engineering degree? Colorado and Nevada schools of mines offer excellent courses.
