well first of all there is no ganster mine in poptropic.
on counterfit island
an hero
nabooti or wild west
no
No.
Not yet.
in the cave in the mine.
at the mine
There is no Diamond Island on Poptropica. There is a Diamond Mine on Nabooti Island. (see related question)
It is near the left on the end but first you have to blow open the rock and the cave and get past the mine carts.
dethes
you have to turn of the power to the electric fence and get a construction hat