If all you're looking for it's credits - just do exobiology - assuming your carrier has Vista Genomics fitted.
High profits, instant gratification - well, as instant as docking to your carrier is and unloading the data to VG - and very very important for exploring the galaxy while dragging around a carrier - no ballast to carry around that will increase your fuel usage.
Mining it is a really bad state compared to what it was before the last major nerfs in the summer of 2020.
Also, IMO, mining is extremely bad for carrier exploration since filling up the carrier with stuff will increase your tritium usage per jump, meaning you will need to mine tritium too and more of it that you'd have to do if you'd keep your carrier lightweight.
But, back to mining - as been said, platinum offers the fastest mining rates so the highest credits per hour, but it's not something you'd be doing in the black since it requires mining in a haz/high res located in a hotspot, preferably as closer to the hotspot center as possible (since the laser mininning yields start to decrease in a noticeable way when you are farther away than 20% from hotspot center)
So IF mining in the black is your thing, as Ian mentioned above, i would advise too to go for the most expensive minerals on the market (monazite seem to enjoy a better demand - and as a result better sell prices - than other like alexandrite, benitoite, musgravite, grandidierite), but again - with the net effect of loading your carrier incuring a much higher usage of tritium per jump
Not as last, for laser mining, hotspot overlaps were badly nerfed in the summer of 2020, to the point that laser mining within 10% of a single hotspot will yield better results than mining an overlap that happens somewhere farther away of the hotspots center. Basically overlaps are worthy to mine only if they happen within the 10% of the center of both hotspots - so, almost perfect overlaps - but even then, mining platinum in a haz/high res in a hotspot is better.
For core mining things are not that bad since nothing was nerfed here (except prices and demand
) - core mining in an overlap will increase the chance to find more cores with the target material while mining in a triple overlap will almost guarantee you get only the targeted cores.However, for core mining the PWA was sort of altered in behaviour and now i find it harder to spot cores than i remember it was back then in the first half of 2020 - but is ok-ish if i can say that.