It cited "adverse geologic conditions" for the decision to cut off production.
On February 13, the mine suffered a roof fall in the 'tailgate' section of the mine. It was thus idled by the Nova Scotia Department of Labour and Advanced Education until an evaluation of conditions could be completed and remediation plan developed.
Several other roof fall events over its years of operation were also found to stem from unfavourable conditions in the mine's geology.
"The mine will not be sealed but maintained by a small staff to ventilate and keep the facility dewatered," the company said.
Donkin was the last remaining active coal mine in the Canadian province. It still had around 481 million tonnes of reserves left, which would have given it a remaining lifespan of between 25 to 30 years.
Kameron Collieries is a subsidiary of the Cline Group.