This is a cross-polarized photomicrograph of a highly altered mineral in a thin section from Bushveld Complex, South Africa. Not sure what it was originally, but it seems to have altered to iron oxides and white micas.
Thanks for your question! I'll have to ask my adviser more about these thin sections, since they're not my area of study. I just went through her collection looking for something beautiful to share. I'll see if I can get back to you on your questions in the near future. :]