These specimens were part of a one-time find in Poland. It is comprised of kidney shaped, white-ish to tan-ish to brown barite xls encased within lustrous, bright, metallic marcasite xls. The piece is polished on one side showing off the intricate barite growth. No damage.
I originally purchased this specimen in Tucson (2016) from Spirifer Minerals. On their website, there is an article discussing this one-time find.