Rare Earth Elements (REEs) are elements that are found in small concentrations in the Earth’s crust. In reality the REEs are represented by 17 different elements. In BetterGeo the REEs are grouped as one element, but come in different colors (they however combine into one ingot). The REEs can be found in skarn deep down in the crust and between different biomes (defined environments) where skarn is present.
The REEs needs to be refined in the smeltery.