I like to use dull copper ingots (and sometimes shadow iron), to get the extra durability and save on POF uses. Then of course, I always mine using prospector tools, even on iron spots, to upgrade it to dull copper.Iron ingots, and dull copper hammer.
And, BTW, a Scorpion slayer will work better than an arachnid slayer on Miasma.
Super slayers do double damage, while non-supers now do triple damage.
This can make it to where you don't have to use enemy of one at all... (and keeps you less vulnerable from being hit for massive damage by minotaurs that way)