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Heat treating rubies and emeralds


I have several inexpensive rubies and emeralds that I would like to
experiment with by heat treating them in my kiln. I can’t seem to
find any regarding the process. Would anyone have
knowledge of the process?


Catherine - These may not be optimal stones to learn with, for two
very different reasons: the rubies are possibly (likely?) synthetic,
in which case they have already been heat treated at much higher
temps than you will be able to easily attain; and essentially ALL
emeralds (above cabbing grade) have been oiled, which makes them
potentially incendiary if you heat them at all. Instead, you might
want to play around with different quartz and/or beryl stones. The
greatest difficulty will be obtaining materials which have not
already been “played” with by someone else.

Jim Small
Small Wonders

I have several inexpensive rubies and emeralds that I would like
to experiment with by heat treating them in my kiln.  I can't seem
to find any regarding the process.  Would anyone have
knowledge of the process?

Hi Cath, First and foremost, whatever you do, keep those Emeralds
away for your kiln!!! Emeralds are a chromium- and/or vanadium-doped
form of the mineral, Beryl, and contain two- and three-phase
inclusions (i.e. solidus, liquidus and gaseous), which can rather
violently explode if heated much beyond 200 degrees Fahrenheit. The
only tried and true methods for improving the colors and clarities
of Emeralds are oiling, impregnation (a variation of oiling, using
resins such as Hughes’ Opticon or other such thinned epoxy resins),
and dyeing with industrial fabric dyes such as Pthalo Green. (I’ve
occasionally seen the yellowish green form used on Nova Era and Sant
Teresinha goods; evidence of the more common bluish-green form often
shows up “crystalized” [in specks] within the colorless epoxy
fillers in the open ends of cracks, in goods from Muzo and Zambia.
If you’d like to know more on the ways this stuff gets there, I’ll
be glad to fill in some of the blanks – puns not necessarily
intended – but you’re probably better off seking out someone who’s
more experienced at dealing with the process than attempting it
yourself. In the end, it’s a matter of the degree of your commitment
to the results; something like that I’m enjoying with metalsmithing,
where it all comes down to how much experimenting you’re willing to
tackle. (The dyes and Opticons tends to leave a truly vile, “burning
plastic” stench in your home or workshop, which lingers on the walls
and furnishings for several days, even despite airing-out with doors
and windows open.)

As for your Rubies, there are several approaches possible, but here
again, the question arises, “How much do I want to try this?” It’s
important to understand that most (if not all) Rubies mined today
are already heat-treated at the mines, before cutting. The reason
for this is that the majority of the world’s cuttable Ruby rough
doesn’t come out of the ground red, at all: it comes out either a
murky brownish-pink, brownish red or purple, or a reddish variation
of those, but with a blue core and a strongly milky translucency. I
don’t and won’t pretend to have so much as a thimbleful of knowledge
on the intricacies of the various forms of Corundum heat treatment,
(especially not when compared to those whom I assume both Dr. Aspler
and Hanuman come into contact in Thailand), but I do know that
differing degrees of heat treatment and different gaseous
atmospheres are used to produce a vest range of enhancements in both
color and clarity, and that not all materials from all locations
respond to heat treaments, in the first place.

For more info, I’d suggest either asking Hanuman for a referral, or
touching base with either Bill Korst at World Gem Resources, in
Minneapolis (612) 926-2924, or the folks at the Montana Sapphire
Gallery (, I believe). I’m sorry that I can’t
be of more service to you, at this point, but I’ll keep digging for
more info for you, and post any new info to the list, when/if it

All the best,
Doug Turet
Douglas Turet, GJ
Lapidary Artist, Designer & Goldsmith
Turet Design
P.O. Box 162
Arlington, MA 02476
Tel. (617) 325-5328
eFax (928) 222-0815