There has been much controversy over the genuinity of red-green Andesine Feldspar, sometimes called Andesine Sunstone, with some noted sources claiming that the material is natural in origin and untreated.  Gemological examination of faceted gems, however, has proved that while the majority of commercially available stones are a variety of naturally occuring Feldspar from sources such as China, Tibet and Mongolia amongst others, they are for the most part pale yellow in colour before treatment, and that the much more attractive orange-red stones with green flashes are the results of copper diffusion treatment. 

There is no evidence of this gem quality Andesine occuring naturally in Congo and buyers should be wary of specimens advertised as being from that source as this seems to be an attempt to deceive.
All gems of this variety for sale at Gemgazer are described as "Cu diffusion treated" and are priced accordingly.

The enhanced gems should not be confused with untreated Oligoclase Sunstone which can have similar coloration and a schiller effect due to natural copper platelet inclusions which are mined most notably in Oregon, USA, although examples of gem quality are rare and valuable.