I'll add my 2p.
Essential to have.
1. Dines.
2. Hamilton Jenkin Maps.
3. Mineralololololgy of Cornwall and Devon (JH Collins)
4. Geology of Falmouth and Truro and the Camborne Mining District, Memoirs of Sheet whateveritis ( very very good). ---as are the others in the series (difficult to get though...)
Worth Having.
1. Morrison (Centrat District, Both vols)
2. Ham Jenks (16 volumes)
3. Embrey and Symes "Pretty crystals book" (forgot the title)
4. Simon Camm "Pretty crystals book, little one"
5. Brown and Acton 5 vols of exploring cornish mines.
6. Trounson, Cornwall's Future Mines
7. Trounson, Cornish mineral industry 19whatever to 19whatever.
8. County Adit by Buckley (See if you can find a copy, I've got one, lol)
That wraps it up pretty well. My Dines is so well read, it's falling to bits. Bear this in mind before you buy a mint first edition.
S