Can diamond thieves sell stolen jewels?

This week, thieves in Brussels pulled off a dramatic jewelry heist of the $50 million magnitude but as they will surely discover, you can't sell these kinds of jewels on the open market and any black market buyer will surely be aware of the same problem. Very tricky, but the thieves have to have planned for this problem, right? Of the past $500 million of art and jewels stolen over the past decade, it is estimated that only 10-15%  has ever been sold on the open market.