More effective than no alloying set

I can tell you that i've seen a 3 bar smelt without an actual alloying set, just a crappy productivity side-effect mining set. This was running 10 ore per smelt, which means 170% yield each time. To get 3 bars, it would need at least 99% left over from before, combined with at least 31% bar bonus per 170%. So from only some productivity it's pretty nice.
Exactly 6.022 x 10^23 worth of Lach molecules.