Protesters have staged a demonstration ahead of the first sitting of a public inquiry into an application for a gold mine in a protected area of Co Tyrone.
There has been considerable opposition to the long-running plan by Canadian mining company Dalradian.
If approved it would see the building of an underground mine with a 20-year lifespan in the heart of the Sperrin Mountains outside Omagh.
Dalradian has applied to extract 3.5 million ounces of gold, 850,000 ounces of silver and 15,000 tonnes of copper.
It is promising at least 350 permanent jobs and a huge economic boost to the wider economy.
The site is in a designated Area of Outstanding Natural Beauty and there has been opposition based on the potential environmental impact to the area.
Campaigners have raised concerns about visual impact, the effect on ecology and protected rivers which run through the area and raised issues of increased traffic, noise and dust.
The company says it will comply with all environmental regulations and will design and run the facility in a way that reduces its visual and other impacts.
One of the most controversial aspects of the development is what is known as the mine waste facility.
It would see up to 4.8 million cubic metres of crushed rock being contoured into the landscape in a long ridge over the lifetime of the project.
The footprint of this waste facility will cover around 28 hectares.
Dalradian says it will use modern techniques and planting to stabilise and conceal it.
Peter McKenna, Dalradian's community relations manager, said: "We've submitted extensive proposals to build an environmentally responsible project which will bring economic and social benefits right across our local community."
Emmet McAleer of the campaign group Save Our Sperrins said local people were determined to stop the development.
"I think when you look at the Area of Outstanding Natural Beauty which is under threat from this proposed toxic development, we want to protect our air, our land and our water and the health of the people and the ecology and biodiversity of the area."
The public inquiry, run by Northern Ireland's Planning Appeals Commission, will hear weeks of evidence on everything from air quality to transport to environmental concerns.
The panel will then write a report and make a recommendation to Stormont's Infrastructure minister. At present that is Sinn Féin's John O'Dowd. Sinn Féin, as a party, says it is opposed to the development.
The minister has the final say on whether to approve the project.
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