Ann: Quarterly Activities/Appendix 5B Cash Flow Report, page-8

An excerpt from the original announcement, possible that there is an extension option though not mentioned!
I don't know the details, only what is announced, I'm not basing anything on assumptions!

(iii) Third Payment: within two years of entering into the Option and upon the exercise of
the Option to purchase the Ellendale Diamond Project, BDM to pay GIB A$4 million in
cash and issue to GIB 7 million fully paid ordinary shares in BDM.
BDM will also pay GIB a 1.5% gross revenue royalty on the diamonds obtained from the
tenements, including during the Option period.
All shares issued to GIB in respect of the transaction will be subject to a 6-month voluntary
escrow period commencing on the date of issue.
Should Burgundy elect not to proceed with the payments to GIB detailed in (ii) and (iii) above,
then (excepting conditions precedent), the Option will not have been exercised and GIB will
retain the Ellendale Diamond Project 100%.