After some testing, it appears Essence Ore (needed for Magical Crops) is not showing up in the new Mining Age; as a result, the mod is kind of unusable at the moment. We’re going to try resetting the Nether on Thursday to fix this… so remember to get your pumps/chunk loaders out of there.
Also, evidently while I was looking Mekanism decided to add copper/tin ores. I’ll push a 1.71 update to address this (no duplicate ores!).