Well, your best bet in getting Hardstones and Sharpstones are the small Phalanxes on the start of 1-2.
Other than that, the miners in 2-1, especially the ones that attack you with bags, are your best bet.
Also, pay good attention to the Crystal Geckos, those are paramount if you want to get some of the Rarer stones. You'll notice that you're close to one when you hear a small chime like a bell in the background. Once you spot one, rush to him and kill him as fast as you can, those little buggers have a tendency to run away when they spot you, and they dissapear a few seconds after running away.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
