When I break a Chisel block in my pack, the block particles that come out are that pink and black checker-board default texture.

My modlist at the moment: https://minecraft.curseforge.com/projects/ben-made-a-modpack/relations/dependencies

I've tried adding and removing Fancy Block Particles, and Unlimited Chisel Works.

It's MultiMine, d'oh. Just in case someone searches for this, just change the first four entires in MultiMine's config from "false" to "true".