Hey Risban,
The idea for this thread is nice, but maybe you should have been a little more specific about equipment.
The first and most important piece of equipment anyone needs before heading into a cave/mine is a friend that stays OUTSIDE! If something happens, they can run for help. If something happens the OUTSIDE friend should NEVER enter the cave/mine. Here's why:
The biggest killer in caves/mines is BAD AIR. A person wanders/climbs down into an area with low oxygen content (One breath of hydrogen cyanide will kill anybody), they will usually be unconscious before they take a second or third breath. They fall where they stood and asphyxiate. The biggest mistake their friends make is run to their collapsed buddy to see what happened, and they drop as well. It happened in the Oak Island Digs.
On 17 Aug 1965, the water filled up the shaft, and the Restall Group ran a gasoline pump to get rid of the water. Dad started climbing down, and his watched as he fell off the ladder into the water at the bottom of the dig. His son Bobby ran to help him and dropped in as well. Cyril Hiltz was the next to try and help, but he too fell victim. Andrew Demont was right behind, and like the others he started climbing down and fell off the ladder into the pit. Leonard Kaizer was next to fall.
A fireman from N.Y. named Ed White understood what happened and stopped anybody else from entering the pit. He tied a handkerchief around his face and a rope around his waist. He was lowered in and managed to save two (Demont and Kaizer) that hadn't fallen all the way to the bottom. Four men died that day, and it was the end of that particular expedition.
If you are going to spend any time in caves/mines, I HIGHLY recommend getting one of these babies:
This is a "four gas confined space detector". It has up to four different sensors for different types of gasses. I use: Oxygen, Combustibles(flammable gasses), Carbon Monoxide (CO), and Hydrogen Cyanide (HCN). Since cyanide leaching was so popular here (SoCal), then the prospect of running into it is very possible. It constantly samples the air, and if the O2 gets too low, or the other gasses gets too high, a VEEEEERRRRY loud alarm goes off letting everybody within a mile know. These things need to be calibrated every year (or more depending on use), and they aren't cheap ($1200-$1400). The replaceable sensors are over $100 each..................... buuuuuuuuuuuuuuut ...............what's your life worth?
Always have more than one source of light (easily accessible in complete darkness), with spare batteries. Wear gloves because handholds can be slick or sharp.
Another BIG thing to worry about when exploring caves/mines is a little ditty we call HISTOPLASMOSIS. It is a fungus that grows in the dirt where there are bat/bird droppings. If you breathe in enough while underground, you can get what is best described as a sort of Fungal Pneumonia. You just feel like you got a bad case of the flu. THAT is the dangerous part! If not identified, Histoplasmosis has a high kill rate. When underground, wear a respirator (or at least a gauze mask).
Also invest in a good form of communicating with your outside buddy.
Those will do for a start.
Best - Mike