Sadly it seems that the Birkhill fireclay mine has been permanently closed as a visitor attraction. I was lucky enough to go round the mine tour a few years ago when it was still open and it was a fascinating visit.
The mine had been in operation from the 18th century before closing about 1980. The fire clay that was mined there was made into bricks for use in furnaces, the bricks being particularly suited for the high temperatures involved.
Unfortunately the mine was permanently closed in 2013, after an extended temporary closure. The closure has been blamed on the high costs of maintenance and the poor state of the buildings. I also suspect that the income from visitors couldn’t hope to cover the costs of operating the place, since several people were needed to give guided tours.
So I got to see something that others probably won’t, which is sad.