BGS say "may be some extension" westwards and state that Minear Downs was primarily an open cast working (pit) and p29 shows 2 shafts between Minear pit and Boscoppa. These may be related to Boscoppa mine.
Hamilton Jenkins maps / 1930s maps already have the aforementioned road in existence.
Dines says the urban development towards the west already existed.
1880s 1:2500 map (oldmaps.co.uk) do not show much indication (none marked) of shafts and workings toward the west of Minear downs (ie Gwallon road). But will try to line up these shafts from the BGS to see where they are on the 1880 and modern maps.
However exploratory shafts, older shafts etc were often not recorded or records were lost.
Gwallon road lead to an area marked as "Slades" on the way to Slades mill (ore dressing?). The 1880 map does not list this as a mine but there are structures there. It seems unlikely to be the shaft at the western end of Minear open mine as it is more South western.
"MINEAR DOWNS TIN MINE
Is situated on an elevated track of land about 2 miles north-east of St-Austell. The workings are open, and have been carried on about 7 years; the returns about 100 tons of tin per annum
Managers John LOVERING and Robert MARTIN Offices St-Austell"
Is it safe to come out of the bunker yet?