Mark, a few things to know about contra luz: it’s a pretty (and)
soft stone for holding up for setting into a ring which will be worn
anywhere near daily; The name contra luz means "against the light"
which means you will not be seeing much of its fire when set into a
ring- contra luz shows up best as a specimen when you are outside in
bright sunlight (think Tucson at an outdoor table. I should know, I
sold Mexican Opals for two years at an outdoor table there) and you
hold it up to the sun and voila- all those magical colors you didn’t
see before suddenly spring to life. I set a beautiful contra luz into
a pendant for my wife and everytime we show it to someone I hold it up
to my flash to show off its colors. Otherwise it just looks like a
boring rock crystal. I feel silly doing this and I’m reminded of my
former days as an opal salesman- and yes, I even had my flashlight
then in case of cloudy days. The stone you are looking for shouldn’t
be too hard to find, although it might be wise to inquire about
anything larger in case the dealer doesn’t have the size you are
looking for, and then cut it down-if that’s what you want to do. I’m
probably stating the obvious. When it comes to Mexican Opals there is
not alot of calibration going on. Most of the cutters in Mexico just
trim the stone and polish for maximum size. I have two dealers I trust
and recommend- Opalos Mexicanos @ 949-661-6735 in Capistrano beach, CA
and Fabio @ Aurea Gems in Mexico city-525-568-5176. Fabio will ship to
the states and he has better prices (generally) than Opalos( sorry i
can’t remember the guy’s name). Best of luck and e-mail me if you
need to. Peter Slone