From what I read natural colour change Andesine is pretty rare and suspicion is that "natural" in a lot of cases means treated by irradiation etc. I have seen alleged colour cahnge Andesine over a carat on sale in the US for less than $100.
London Blue Topaz ring tonight - 7 carats lump or so in flimsy gold shank. Start price of over £900! Topaz is like quartz. It's a white uninteresting stone -cheap as chips and treated and flogged as Swiss, London or Mystic . Nice shiny stone but £900? You're having a laugh. :giggle: