Western Areas chairman Terry Streeter and director David Cooper will appeal a Supreme Court decision that awarded nearly $65 million to unrelated company Western Areas Exploration.
In July, Justice Eric Heenan found in favour of WAE which claimed a nickel opportunity was taken away from the company by Messrs Streeter and Cooper earlier this decade.
Mr Streeter said he was confident there were strong grounds for appeal.
"In my view the result is wrong, and I am confident that it will be reversed on appeal," Mr Streeter said in a statement.
"I have always felt that the plaintiff's claim was opportunistic. I was extremely surprised and disappointed at the trial result and believe that the Judge has made a number of errors."
"We have formally commenced our appeal, and now have five weeks to further develop and finalise our detailed grounds and written submissions to the Court of Appeal" he said.
Mr Steeter said he believed Justice Heenan's decision also had wider industry implications.
"In my view the decision will serve to encourage similar claims, and is likely to make skilled directors reluctant to invest their personal time, expertise and capital in support of development projects.
"For an industry like mining in Western Australia, which has traditionally been driven by exactly that kind of support, the outcome is a real concern."
