Here is a link to the Province article about Slumach. Its a bit to Waite focused but if you want to try for his location its in the Upper Pitt River north of the Hotsprings.
In regards to books on the lost mine here is a list of books that mention the lost mine or are totally about it.
1. Slumachs gold In search of a legend by the same authors above this is there first edition 1972
The chapter Remants of Research is most interesting.
2.Tales of the Golden Ears by Don Waite
Tells the Amanada Charnley Story same as article in the Province.
3.The Golden Mountains by Charles A miller
Full of great info like the Shotwell Story (who the Jackson letter was adressed to)Also has accounts of a prospector finding gold around Debeck Creek and has an account of Ragner Berglands fall into Spindle Canyon when he was attacked by a bear. As well as all kinds of other info on the mines around Stave Lake and Blue Mountain. Two of which I own for the moment.
4. Jack Mould and the Curse of Gold by Elizebeath Hawkins
(Pile of crap about Jack Moulds find at the North of Bute Inlet. Claiming his location was Slumachs gold. The worst piece of crap ever to be published regarding Slumach. If Slumach placed a curse on the gold. Lets hope he placed a second one on this book from the grave. The only thing good about this book is it mentions Jim Everett. A great dowser who found Jacks gold for him on Southgate peak near Bute Inlet and Jack took the credit and didnt give Jim a dime. Jim is a great man. May he rest in peace. However that being said Jack did find a mine (adit) on Southgate peak and an old Spanish helmet. I believe he did in fact find an old Spanish Mine. But there is no connection to Slumach. The last time I had a line on this story. Jack himself had come to the conclusion he had not found Slumachs gold and was focusing finding info connecting it to the Spanish in the Archives in Seville. He found a document claiming a wreck went down loaded with ore somewhere in Bute Inlet. That had come from the mine on Southgate peak.
5. Seekers of Gold by Daryl Friesen
(My own account) You can read some Chapters online and be the judge.
6. The Fraser Valley Story by Don Waite
( First release of Stuart Brown Letters to the Public and mentions tent shape rock found near Corbold Creek.
7. Slumachs lost mine by Ramsey (fiction)
Sounds like Lara Croft meets Slumach (crap)
8. The lost mine of Pitt Lake by Bill Barlee (an article but a must)
First release of Jackson letter to public. Bills father got it from one of the searchers who found it in Volcanic Browns last camp.
9. The Lost Creek mine by T.W.Patterson availble in Lost Bonazas of Western Canada Vol 1
A great account with all kinds of little pieces of info to help one put the puzzle together.