This strange calcite on amethyst specimen is still unique, 30 years later. It was mine, and I purchased it as a young collector when in college sometime in the early 1990s, for my own calcite collection I was quite proud of at the time (it had over 500 specimens, all different). I was fascinated with this for several reasons. Firstly, you almost never see rhombohedrons from Brazil, let alone these complex modified rhombs that look more like calcite from Denton Mine in Illinois than anything Brazilian. The amethyst proves the origin, or you would have trouble believing it. The crystals are GEMMY, transparent, and brilliantly lustrous, sharply twinned as well. I believe the small specks are minute hematite crystals, but I never analysed them. Overall, it is simply such a shocking combination - at least, for those of us in tune with calcite associations and rare styles, that I bought it immediately and it has been in my collection ever since (although I sold my old collection in 2005, I later bought it back in 2010 and so maybe it never sold... technically?). This is an old old piece from long ago and as you can tell, i am quite enamored with it, having never seen another like it.