No hurry at all really. Crystallising the loss is really only necessary for end of this financial year - June 2017.... that's when you can offset tax on any gains you might have with your MBN loss.
In the meantime though, they might sell the mine for enough to return something to shareholders. Or they might also officially announce the share are worthless - which means you don't need to pay delisted to crystallise the loss anymore.
MBN Price at posting:
8.3¢ Sentiment: None Disclosure: Held