I have bought several minerals to crush and mix with resin, but I haven't found anything cheap and with malachite green, my favourite, it costs about £10 just to make about 4 blanks with malachite, never mind the resin, moulds and time to make the blanks. At least when I make them I know they are unique(ish) and they are not in the mass market. I don't know how the ones you bought will look when turned, but I am looking forward to seeing them.
Peter