These are colour additives which are insoluble in the medium to which they are added (do not dissolve in water or oil). They are generally very stable and do not bleed or migrate and are therefore very popular for soap making as they are also very cost effective. They do however have a tendency to clump so they need to be mixed very thoroughly in oil before adding them to your soap base. If you wish to use these colours in melt and pour soap base you will need to mix them with glycerin first otherwise they will cause speckling.
Oxides and pigments are usually cosmetic grade and can therefore be used for mineral makeup and soap making as well as crafts