CosmoTheCosmicCat

I am also getting this issue. Other materials, like starmetal seem to work fine, but rock crystals and celestial crystals do not seem to be able to be inserted into...

Were any grindstone recipes changed?

I would say Flan's mod should be kept out. Part of the reason the 1.7.10 pack takes so long to load is Flan's mod due to how horribly optimized it...