Praseolite, or "greened amethyst" is a common treatment of certain
sources of amethyst. I am guessing that they're treating the material
that's too pale or brown to sell well. Oro Verde quartz is rock
crystal from one mine that's been irradiated and then heated, much
like most of the strongly blue topaz. You should also be aware that
synthetic green quartz is commonly available. The lemon quartz is
most likely treated also. Right now, given the market, you have to
assume that any gem is treated unless specifically stated otherwise.
However, there have been a few occurances of green quartz reported
in the literature.
Richard, in dry windy Michigan