I have seen the cranes many times but could not remember the dates of working.
A posting in 2009 by Sougher (the late Margaret Howard) on this website gives some details:
https://www.aditnow.co.uk/community/viewtopic.aspx?t=2500 I have spoken to my old spar mining friend whom I have known since 1956, many times about Tearsall. He comes from Elton is now 76 and has been sparring since he was 17, his two uncles were spar miners and one had a processing plant at Portaway mine. He's worked at many sites including Bonsall Moor, Tearsall, Jugholes, Low Mine, Masson Hill, and Moss Rake etc. etc.. He has always said that there is hardly any fluorspar, if any, at Tearsall, the main mineral found there is calcite. He always contends that the Peak Park was duped into believing that fluorspar was found at this site, in order for the owners to work the limestone and turn it into a limestone quarry (perhaps planning wouldn't then have been granted in the first instance) - much of the limestone quarried was transported eastwards to the sugar beet factories in Lincolnshire. He says that fluorspar was found at Ashover, Crich, Masson Hill but gave way to calcite the futher west one moved away from Masson Hill. When it was first opencasted we used to visit the site and found very large specimans of dogtooth calcite at Tearsall, we found very little evidence of fluorspar, the dark blue variety was found more in the centre of the Moor. My friend worked on Bonsall Moor (he was responsible for buying the two little dinosaur cranes which have been abandoned on the Moor)and with two partners he excavated the open rake that can be found on Bonsall Lees. White Low (where workings can be seen) further to the west on the Moor, is called White Low because of the high calcite content of the vein. If my friend is proved right and hardly any fluorspar deposits are found, will the Peak Park then stop the workings? It would be very interesting to know.[i]