The diamond industry’s collapse last year left the biggest producers with billions of dollars of uncut gems stashed away in safes. Now, in a matter of months, they’ve suddenly found buyers. The huge stockpile was built up when the diamond world came to a standstill during the height of the pandemic, stoking fears that gems amassed by the biggest miners could hurt the sector for years. But rampant demand from the middlemen who cut, polish and trade stones has all but wiped out the stash — and remarkably as top producers De Beers and Alrosa PJSC raised prices.