Can anyone tell me if Russian Pyrite (rainbow pyrite) is color
Hi Gary, The color is definitely natural: I have seen it in situ
within large geode halves. However it can fade, although not for the
reasons you'd probably expect. I learned the following from a stone
cutter a couple of years ago.
It was commonly accepted that the bright colors often seen in
rainbow pyrite were not permanent because, by the time the material
had gone through the cutting process, most of the colors had faded to
pastel greens and oranges. Eventually, some bright-eyed lapidary
realized that the color change only occurred after the stones were
left to soak in soapy water -- a common practice for cleaning them
after cutting. It turns out that the fading is due to water, not
other factors, and can be avoided by not soaking this material. You
can use soap and water to clean it; just don't let it sit in water
any longer than necessary.
I've used a lot of brightly colored rainbow pyrite in my jewelry and
never noticed any fading, even under the halogen lighting I use in my
show booth, though I couldn't swear that it would never fade if left
out in bright sunlight.