Antler pickaxes are the first pickaxe, have little durability (100 ) but you can craft a bunch of them if kill again the first boss , next are bronze and iron tier that have a lot more pick damage and durability
Copper nodes are bigs green with yellow veins boulders in black forest you have to star mine in the edges until you cant go any more underground , you have to do this because the nodes continues underground ( a full mined node can give you 120-130 pieces of copper , mine only the "crown" like 50-60 )
Tin are little nodes in black forest shore , easy to get and mine , 3-4 pieces for each
Iron is easily found in sunken crypts in the swamp after beat the second boss , its mined from "scrap gates" that stop you way to advance in the crypts , can also be found in chest inside crypts
Silver are in big boulders veins underground in the mountain , iron pickaxe are needed to mine it
Black metal are dropped by goblins in plains and inside chest in goblin villages