The conveyance cage that takes workers down a mine shaft and back to the surface is generally one of the safest places to be underground. That's one reason the Impala Platinum disaster at its Rustenburg operations, the worst in South Africa in more than two decades, is so shocking.

When being hoisted to the surface at the end of a long shift underground, a miner generally breathes a sigh of relief. The dangers that lurk in the depths recede as the "cage" -- which is what it effectively is -- ascends to the surface.

On Monday afternoon, 86 Implats mine workers would have been looking forward to returning to the surface and taking a shower. They were spread out among the three levels of the cage, which has a capacity for up to 145 workers. The miners in the bottom level of the cage were unaware that they were in the worst place possible.

Shortly before 5pm on Monday, Implats says, the conveyance lift in 11 Shaft -- which is about 1,000m deep, with operations across 20 levels -- began its scheduled ascent to 17 Level.

"The conveyance unexpectedly reversed direction and began descending back down through the shaft. The emergency protocol for such an incident was immediately and automatically activated. Regrettably, although the winder rope remained intact, the emergency protocol failed to immediately arrest the lift's rapid descent," the company said.

The winder counterweight became snagged for some reason, which resulted in what Implats described in a statement...