I am not a mica expert. I do know I have seen different grades of mica though. Most you see on soapmaking supply sites will either be soap/body grade or a higher grade for lip/eye useage. So yes, there are different grades which means all micas are not created equal.
I suggest that you be very conservative in choosing soapmaking ingredients from non-traditional sources. Various of our ingredients are food grade or cosmetic grade, and all our sources guarantee our ingredients are safe to use in soapmaking. But if you get an ingredient from a source that makes no particular food or cosmetic claims you should assume they have no guarantee and would be risky to use.
I've been trying to find rosin for transparent soap, and I can't find a single source that makes any claims about the purity of the rosin. Rosin can be used in incense safely but there appear to be no food or cosmetic rated sources. Rosins are also used to wax the bows of musical instruments. Here too no claims are made, and the rosin is expensive. I'm glad that rosin is an optional ingredient, although its scent and color properties make it a very nice ingredient. Having no safe sources I'll have to forgo rosin.
Note that it is not unheard of for artist pigments to be toxic.