It's not so unusual. I can recall major pit wall sloughs at Bingham Canyon and Freeport Grasberg, and likely hundreds of minor ones over the years. Mine designers try to improve pit profitability (less overburden to remove per tonne of ore) by steepening the pit walls almost to the point of slope failure. Sometimes nature comes back and bites them.
The Bingham Canyon failure was captured on video.
https://www.mining.com/bingham-canyon-mine-slope-failure-37216/
The Freeport one is not so well documented on the web because of Freeport McMoran's fixation with secrecy. Photos do exist though, IIRC the material that sloughed at Grasberg was of something of the order of 50 million tonnes.
Doubtful. All the other producers will lick their lips and up production.