William Donnelly took action over the decision to approve underground work on the site at Cavanacaw, near Omagh.
But the Court of Appeal dismissed claims that more than 20 hectares at the location was never properly assessed.
Lord Chief Justice Sir Declan Morgan ruled that features within the planning application process “overwhelmingly identified” the full scale of the project.
Following the verdict Mr Donnelly said he is now considering mounting a further challenge to the Supreme Court in London.
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Mining has been carried out at the site by Omagh Minerals, a subsidiary of Canadian firm Galantas Gold Corporation.
In 2015 the then Department for the Environment minister, Mark H Durkan, gave the green light to the extended project.
Planning permission was granted for underground work at the existing mine on the basis of compliance with strict environmental conditions.
At the time Mr Durkan said these would include progressive restoration of the above ground site to ensure the protection and enhancement of habitat over time.
But Mr Donnelly, who has shares in the goldmine, claimed there was an unauthorised removal of large quantities of rock.
Part of his case centred on the environmental impact and possible acidity of this waste rock.
Points were also raised about the size of the site being either 60 hectares or 81 hectares.
According to Mr Donnelly that raised the possibility that the minister was “misinformed or even confused as to the scale of the project being approved”.
Lawyers for the department countered by insisting work was already covered by previous planning approval obtained more than 20 years ago.
No regulations were breached during the decision-making process, they argued.
In September last year a judge dismissed Mr Donnelly’s initial challenge against the minister’s decision.
He appealed that verdict in a fresh attempt to have the approval quashed and a new planning process undertaken.
Mr Donnelly contended that while planning permission was issued for an 81-hectares site, an environmental and habitats assessment was only carried out in respect of 60 hectares.
But the court held that the content of an environmental statement dealing only with 60 hectares displaced the conclusion that the application site comprised the larger area.
Sir Declan found that “approved drawings overwhelmingly identified the application site as comprising 81 hectares, 60 hectares of which was the open case mining operation and 21 hectares of which was blanket bog”.
He confirmed: “Accordingly, in so far as the appeal sought to overturn the decision not to quash the planning permission, it must fail.”
Outside court Mr Donnelly said he was “seriously considering” seeking leave to appeal to the Supreme Court.
“This has always been about ensuring Planning Service do their jobs,” he added.
“I’m a shareholder in this goldmine, and have been for 25 years, I’m not anti-development.”