Your experience doesn't seem to follow the general
experience of the gem trade or the jewelry trade
Hi Don; I don't want to seem contentious, but I'm not
pulling this out of thin air.
To add another voice of experience (30+ years) to this debate, I'll
side with David here. Remember that garnets form in contact
metamorphic zones, much the same as do sapphires and other such.
Temperature itself is not usually a problem. As with many other
stones, it's not the temperature itself, but the sudden changes
thereof. If you take your time so the stone is raised in temperature
gently, it will much more likely withstand the process. I've more
than once seen garnets, usually common dark red varieties, with a
bit of torch damage consisting of melted facet edges, but no actual
fracturing from the soldering heat. And i'd remind some that one
used to be able, and may still, be able to buy a soldering board, as
well as a variety of soldering sand that is simply garnet sand. It
holds up very well through repeated use.
When GIA puts out those charts, remember that they must err on the
side of extreme caution. If they listen to the above experience,
which they're well aware of, and say garnets can take some heat, sure
as shooting some idiot will take a torch to a 20 carat gem quality
tsavorite and split the sucker into pieces. And since the dangers of
heat shock increase with the size of a stone, Almost ANY large stone
has to be treated with care, even with just the steam cleaner. Keep
in mind that those charts are used by a lot of otherwise totally
untrained and uninformed and gemologically naive sales clerks, many
of whom know which stone is which only be reading the price tag. I'm
certainly not saying sales clerks are all idiots, most aren't in
fact. But there are enough of those part timers in the mall stores
that do fit this, and for whome the only source of may
the chart from GIA that the manager stapled up by the cleaner, that
GIA really has to report the worst case situations on the gems, not
the most likely situation.
Garnets are not immune to heat damage. But many varieties seem to
be fairly stable in color with heating, and if the heating is gentle
and at least a little gradual, and the stone is not badly included,
then more often than you'd expect, they'll survive considerable heat.
At one point way back in school, I played with casting stones in
place in silver setting. About 2/3ds of the attempts with garnets
worked without damage to the stones.
And most goldsmiths you might ask, I think will be able to give you
similarly mixed memories, suggesting that garnets, while not immune,
are also not instant casualties when heated. So the "general
experience of the gem trade or jewelry trade" kind of would depend on
just whom you ask, and how you phrase the question. If you ask, are
garnets ever damaged by heat, the answer is of course, yes. If you
ask, do garnets sometimes survive being directly soldered on, those
who've tried it will also say yes. Just be gentle, don't point the
torch directly at the garnet, but rather tangent to it, just
brushing the metal, not the stone itself. And for heavens sake, let
it gently air cool. don't quench. And do this only with stones you
can afford to replace if it doesn't work.