The application was declined because the "irreparable damage to an area with very high, unique and nationally significant conservation values" outweighed the economic benefits.
"The Te Kuha area is one of the last two areas of intact, elevated Brunner coal measure ecosystems," Sage said.
"It is an undisturbed area which is precious and unique, and supports complex and diverse habitats for threatened plants and wildlife including great spotted kiwi, land snails and lizards."
Sage said the area was untouched and mining would cause irreversible damage.
"Under the Conservation Act, this land is held to preserve and protect its natural and historic resources. This application is inconsistent with that purpose."