The deal is worth A$1mln and the AIM quoted firm will receive payment in shares: 1.3mln new shares in GOS priced at 40p each.
Xtract expects to receive the shares in seven days, and it will result in the company’s stake in GOS increasing to 7.6%.
"Having taken the decision to direct Xtract towards near term mining production propositions, we welcome the purchase of the royalty for our non-core GOS Group investment,” said chief executive Jan Nelson.
“We have a significant stake in the GOS Group and have every confidence in their management team to realise value for shareholders.
“With the current number of GOS shares in issue and at the latest placing price our position has a value of £2.95 million. The early exercise of this option, in our opinion, demonstrates the confidence that the GOS Group have for the future prospects of Julia Creek."