I suppose that most of us have been in a commercial cave at some point. You know the ones with the stalactites (from the ceiling), and stalagmites (those rising from the ground). You walk on limestone if dry or on a wooden boardwalk if wet. Some of us have been in a real mine on a tourist visit. I know of a good gold mine in Cripple Creek, Colorado, that I took my wife down 1,000 ft and walked around. Here the gold mineral is silver looking because the gold is a gold telluride.
I doubt that many of us have been down in a working mine. I had a brief career doing so. The only reasons that I think a non-miner would want to do this is curiosity or that they are not permitted to do so. My longest bout of working in a mine was in 1957 at the Balmat #2 mine* at Balmat, New York, which, at the time, was America's largest zinc mine with an ore of sphalerite (zinc sulfide) in marble, but, as underground mines go, was only a medium-sized mine. I was collecting samples for a Ph.D. thesis in geology so I had the run of both active and inactive parts of the mine. I was working for the, now defunct, St. Joseph Lead Company whose main properties were in Missouri with an ore predominantly of galena (lead sulfide).
Since I was being paid, there was a thought that maybe they could get something good from me. They settled on my trying to see what geological information I could recover from the stopes* * (large rooms from which ore was removed) shot out in WW-II. At that time they mined as fast as they could, following the ore, with no record kept of the geology. When I would go underground I would sort of deaden my senses as the moldy stench issued from the inclined shaft. I would get off the hoist at the appointed level, maybe 500 ft, and go to the floor of a stope, a void that was maybe 200 ft deep, 200 feet across, and 500 ft long. I had to use a compass to navigate my way across a stope, to record the geology on the other side, because there was so much moisture in the air. I would have to climb over or find a way around large blocks of marble, a cubic yard or more in dimensions. Some of these blocks had dust three quarters of in inch deep, some a quarter inch and some were clean.
My rational self told me that, if a block came down while I was in a stope, the probabilities were that it would not land where I was, but my emotional self didn't believe it. Though the temperature in these stopes was around 55 degrees and at no point did I ever feet hot, I would come out at noon or so dripping with nervous sweat.
In more modern stopes, there were pillars to hold the back (roof) up and every once in a while there would be a loud BANG! A "bullet" of marble would be shot off from a pillar from stored up stress in the rock during marble formation. A limestone formation for some reason would be taken down thousands of feet into the Earth where it became hot and under high pressure. It became plastic and shear stresses folded and refolded and maybe folded it again, but at some point it gradually rose to the surface through uplift and erosion. All the folding and refolding made following the geology to be difficult. I think that if you ever were hit by one of these "bullets," it could kill you, but I never heard of anyone hit. Again the probabilities were with you. My boss was in the Balmat #3 mine talking to a miner at the hoist entrance when a cubic yard of marble fell killing the man he was talking to only a yard or so away. Mind you, the hoist area is supposed to be the safest place in an underground mine. But overall, the Balmat mines were really safe with little timber work needed. If you see timber is used in a mine, you may think that is a safe spot, but actually it is a dangerous spot because timber wouldn't be used if it was safe.
Once when I was in the active part of the mine, I heard the loud hissing sound of compressed air used in the drilling equipment, a sign that a charge was going to go off to break up the ore for mining. Because of the echo, I couldn't tell where the hissing was coming from, and, as I ran around the passages, my God, I realized I had come right upon a face of ore where I could see the wiring and holes for blasting. Damn, I had gotten myself right in front of the blast so I quickly turned around and franticly ran away. Luckily the charge didn't go off while I was at the face, but you can bet my heart was pounding fiercely.
At the Edwards mine some miles away from the Balmat #2 mine, there were Y-shaped stopes. Several of us were in one of these one day, several thousand feet underground, when we heard of block of rock bouncing its way down one of the limbs of the Y. There was an echo and we couldn't tell where the block was coming down so we ran out of the stope. My boss fell and was sliding along the wet muck, his right arm up in the air when by accident he caught a cable protecting a winze (an underground shaft) dropping 200 ft. Fortunately this stopped his slide or he would have gone down and certainly been killed.
For a year after my underground experiences, I was very sensitive to any cracking sound, such in a building cooling at night in the winter. I would flinch and quickly look around. I suppose today you would say I was suffering from post traumatic stress disorder.
* http://instruct.uwo.ca/earth-sci/fieldlog/Grenville/balmat.htm
** http://en.wikipedia.org/wiki/Stoping_(mining)
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