The NSW Planning Assessment Commission has refused consent for a coal mine planned for Gloucester, potentially culling a second major mining venture near the mid-north coast town in less than two years.

The commission found the economic benefits of the Rocky Hill open-cut coal project sought by Gloucester Resources Ltd would be outweighed "by the detriment to the quality of life for residents near the mine site".

A protest sign in Forbesdale, near Gloucester, opposing the proposed Rocky Hill coal mine. Credit:Liam Driver

"In balancing both the benefits and adverse impacts, the commission finds that the project is not in the public interest," it said in a statement released on Friday.

The PAC's determination was welcomed by Groundswell Gloucester, a group that helped lead the successful opposition to a proposed coal seam gasfield that was dropped by AGL almost two years ago.