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Heating "red, white & blue" stones

Dear David, It occurs to me that David Gellers’ generalization about
red, white and blue stones being heat resistant is a recipe for
disaster. There are many stones in those colors which cannot take
heat. I was once on a buying trip in Brazil when I bought a fabulous
red, white and blue tri color tourmaline. I wouldn’t have dreamed of
getting heat near such a stone inasmuch as tourmaline is notoriously
fickle and very often can’t even be cut across the color change
boundary ! Then there are the other stones which occur in red,white
and blue and which have highly variable resistance to heating. The
spinels are a good example as are garnets. The truth of the matter
is that all stones have varying heat tolerances and may further vary
according to origin. The stones from one mine can be sensitive and
those from other mines can be heat resistant. Trace elements and
included minerals can have a big bearing on heat resistance as well.
And, even within the diamond, ruby, sapphire realm, heat resistance
can vary. Then, of course, there is the consideration of RATE of
heating. Many stones will take slow, controlled heating as in
casting with stones. However, the rate at which heating takes place
will vary with the stone and, of course, some stones will change
color when heated. The moral of the story…be careful about
generalizations when it comes to natural objects; Mother nature
seldom uses the exact same recipe ! Ron at Mills Gem, Los Osos, CA.

One little detail to add, because Moissonite is double refractive,
using a loop, look through the kite facet at the culet, if you see
two of them, it’s a Moissonite. Only one? Then its diamond or CZ.
Just a quick check that is very useful.

Joel Retzlaff
Liquid Jewelry