It's very grindy until you get your first activator, then you can leave it munching away while you do stuff. Currently on 4 activators on a 3 sieve system (2 on gravel, 1 on sand, 1 on dust), and in the time it took me to build multiple smelteries to process all the materials, I've got enough emeralds to keep expanding. Not sure yet if I need to expand the sieves beyond the 3. Feels like it's producing more resources then I could possibly ever use (and I'm aware there are quests for gathering stacks of ingot blocks).