I get the small yellow ones for the goats, and the sheep like that one. I think the red coloured one has copper in, so not to be given for to sheep. If you look on the label, it does say if there is copper in them. They also come in mint and carrot flavours, which my horses like. Sometimes the goats lick and lick them, and break chunks off......so they do not last long.
I think the small ones are around £2.50. You can get a giant sized one, which you can put string through the middle and tie to a gate or fence post, and those last for ages.
Having said this, if the goats, sheep or whatever are fed a mix, its usually got minerals in that.