Primary Test: Magnification is the key in most cases. It is rare to find one of the diffused andesine without some kind of tell-tale inclusion. The most common is the lamella twinning formations that are grossly over extended, and many be filled with residual flux material from the heating process. These engorged and filled lamella formations will be diagnostic in most cases.
Secondary Tests: The immersion cell will be very important as a confirmation tool. Many of the Thai treated andesine will have a green core and red outer rim. This is a reverse of what is expected in copper based feldspar as the copper will be red inside, and turn green due to oxidation around the outer rim. So the green interior and red exterior in an immersion cell will be diagnostic for the diffusion treated andesine. Also to be found with the immersion cell are color variations due to the diffusion process not coloring the stone uniformly. We see this in diffusion treated sapphires, and in beryllium diffused sapphires. When gemstones are diffused with coloring elements there is no way to make the coloring elements diffuse into the stone uniformly. The result is an unnatural looking coloring of the stone that is best seen with an immersion sell under magnification.
Repair and Setting: Heating is not recommended with this diffusion treated andesine as the diffusion process itself is not fully understood. Heating of the treated material could cause expansion and breakage. Due to the porosity created during the treatment process, cleaning in an ultrasonic or cleaning solutions is not recommended.