I've already contacted the North of England branch of the Institute of Quarrying to see if I can find out anything more about this stone. On the website where I found the picture it did say that this stone was a popular choice for sharpening razors in the past. I just want to know if the stone was mined and retailed and thus an article of national commerce or if it was just a local thing, in which case I'll be going straight to the mine and extracting some of the stone myself.

Regards,
Alex