Since q_x hasn't substantiated that comment, I'm going to assume it's not substantiable, any more than his statement that the green filaments are produced by the action of light on dichromate, sui generis. It just doesn't happen that way, as I explained.
Originally Posted by can
The kneejerk assumption one might make is that the green filaments are chromium oxide, but as I said, without knowing what impurities you're dealing with and how they're reacting with the dichromate, it's impossible to know that. There are, in fact, two chromium oxide pigments, neither of which is particularly precious; one is PG 17, chromium oxide green, sometimes marketed as "olive green" (although "olive green" usually is reserved for a mixture of pthalo green with various yellows and rose-colored pigments). Chromium oxide green is a dull green, weak pigment, not terribly useful in gum printing, and one of the cheapest pigments available. The other is viridian, PG 18, also a common pigment, not very expensive. There are no other green chromium pigments I am aware of, precious or not. But as I said, I'm always open to being educated, if someone has better information.