My horses have a choice of a white block and a red mineral block in each of their stalls.
My "blocks" are in holders, not in their feed buckets.
I find putting the salt blocks in the feed bucket makes them crumble, break and then my horse won't finish their feed as it is to salty.
Neither of my horses has ever appeared to have a sore tongue from licking a block....
My horses do lick their blocks as I replace them pretty often. I don't do loose salts either..
Having the 2 types of salt allows my horses free-choice of what they want, when they want it and need it....
My horses are in pasture 24/7 but have free-access to their stalls all the time...they come in every day for fly-spray applied and feed anyway.