Asbestos is a fibrous mineral comprised of short barbed threads. When it is in a solid form it's highly heat resistant and fairly chemically inert. The problem is when it becomes aerosolized (eg dust kicked up by walking around) it sticks to your skin and clothing becoming an irritant (think like fiberglass itching). Worse still is when (not if) you breath it into your lungs, those barbs act like fish hooks trapping the fibers in your lungs basically forever. Over the years these fibers will cut and irritate your lungs causing scar tissue (Asbestosis) or cancer (mesothelioma) or both. In the case of mesothelioma, once it develops the survival rate is only 23% and is a horrible, painful death; typically in less than 2 years.

Under no circumstances should you go anywhere near a known source of loose asbestos like at a mine. That mine ran for 60+ years and will have dangerous amounts of dust virtually everywhere that someone would consider "interesting". Dust masks/N95 will not provide protection and even something fancier like a 3M P100 is not intended for that level of exposure (it's meant for limited exposure like what you might get renovating an old house that "might" have asbestos, not exploring a mine that does have asbestos). Workers who deal with asbestos (such as for asbestos abatement projects) will wear full body clean suits, including sealed gloves and boots as well as negative pressure air-purifying respirators.