This is one of those weird minerals that, having never seen one for sale and finding the name unpronounceable, I admittedly just bought on trust that it is as rare as my supplier thought. I got it from Josef Vajdak of Peque Rare Minerals, in response to the usual "show me something neat and rare" question I ask him at shows. He says it is really good for what it is, and I will cede to his wisdom on the point. Josef is, after all, one of the better known Czech mineralogists and has a Czech mineral named after him, even. So, I figure he knows his minerals from the region! Comes with a copy of a scientific article on the find (in Czech) and an XRD analytical result set including photographs and data. (FYI..i paid $450)