BBCThe Glan Lash opencast mine opened in 2012 and closed in 2019, but plans were submitted to extend the siteThe last outstanding proposal for opencast coal mining in the UK has been rejected.
Carmarthenshire council refused plans to dig for 85,000 tonnes of coal at Glan Lash mine near Llandybie, citing impacts on the local environment.
Bryn Bach Coal Ltd had wanted to extend the site over 10.3 hectares (25 acres), promising 11 jobs.
It is the second time the company's plans have been turned down since the opencast mine closed in 2019. BBC Wales has approached the company for comment.
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In a decision notice uploaded online, Rhodri Griffiths, the council's head of place and sustainability, said the proposals would conflict with a number of policies on biodiversity and the environment.
Protected woodland and hedgerows would be adversely affected, he said, and the scheme would result in "the unacceptable disturbance, degradation and loss" of "irreplaceable peatland".
There were also concerns for a local population of marsh fritillary, one of the UK's most threatened butterfly species.
The mine opened in 2012 on a licence permitting the extraction of 92,500 tonnes of coal over four-and-a-half years.
The company had revised its latest extension plans, after councillors rejected previous proposals in 2023.
The mining firm said there was considerable demand for its "premium quality anthracite" coalJenny Lloyd, of Friends of the Earth Cymru, said the council's decision was "great news".
"This brings to a close years of campaigning, but it also brings a stop to Wales' last opencast coal mine," she said.
"It's an opportunity now for that land to be remediated for nature and the community."
Coal Action Network said there were now "no live applications for new coal mines" in the UK and that the decision reflected "a clear, strategic commitment to climate leadership, rare habitat protection, and safeguarding the health of surrounding communities".
"We'll continue to engage with the local authority on the restoration to ensure it is delivered to the standard promised," added Daniel Therkelsen from the campaign group.
Carmarthenshire council said the application had been refused as it was contrary to the policies set out within Carmarthenshire County Council's Local Development Plan.
Bryn Bach Coal Ltd has been asked to comment.
In its application, the company had argued it had developed "a niche non-thermal market for premium quality anthracite".
It said there was considerable demand for its coal from industries ranging from water filtration and battery production to green steelmaking.
The company has six months to appeal the decision.
The UK's largest opencast coalmine - Ffos-y-Fran above Merthyr Tydfil - closed in 2023 after its operator's application for an extension was turned down.
Opencast mining involves scraping rock and earth away at the surface to recover coal - creating an open pit, rather than digging deep underground.
Wales has one last remaining deep mine - at Aberpergwm, in Neath Port Talbot.
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