This is a copy of an article which I wrote a couple of years ago and posted to the USFG list. The information and procedures I have collected over the years and offer my findings here. I would certainly be willing to include any further suggestions that have proven helpful in keeping our Tourmalines in one piece throughout the faceting procedure..

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M. Louis Lemery, in 1717 concluded that tourmaline was magnetic and that
the magnetism could be induced.

Franz Ulrich Theodor Aepinus, concluded in 1756 “that not only friction
but heat also should develop the electric energy, both positive and
negative, of the tourmaline”(sic).

Since 1921 when piezoelectric minerals were first explored, tourmaline,
which is strongly piezoelectric has been used in gauges to measure
transient blast pressures.

We know that when piezoelectric material is distorted an electric and/or
magnetic charge is produced and vice versa piezoelectric material distorts
when an electrical and/or magnetic charge is applied or induced.

With tourmaline we know that distortion is not the only means of producing
a magnetic and electrical charge, temperature change, friction and
abrasion also do this. The effect however differs in strength and polarity
and of course will cause the crystal to distort according to that strength
and polarity. How much crystal oscillation we have going on at the same
time as cutting or more importantly, polishing will be a significant
factor in the failure rate.

Another source of failure is the rind. I find this term a bit of a misnomer
as we tend to think of a rind as the outer skin of something that is
growing inside. A crystal grows by deposition so the ‘rind’ is the newest
part of the stone, the core being the oldest. Now we know that the
crystal is formed over long periods of time and we know that it requires
heat and pressure, we also know that the tourmaline crystal will deform in
response to that heat and pressure whereas the new deposition will not be
so stressed.

As the crystal grows there will be unstressed growth covering stressed
growth until the heat and pressure changes and another cycle of growth
occurs. Flawless gems will only occur if the temperatures allow the
crystal to anneal as it grows. This does not necessarily mean that the
last growth was annealed when the stone was mined so there is every
possibility that just below the unstressed newest layer lies a crystal
core that needs to relax.

THE TOURMALINE PROCEDURE

Removal of the outer layer is universally recommended.
Using hand held dops to do this has been strongly suggested.

That all grinding and polishing should be along the length of the crystal
not across it, using fine grit freshly charged laps is universally
recommended.

The crystal has one end designated the head and the other the tail. All
cutting and polishing will be in the same direction. This means you need a
reversable motor to accomplish this. Many say you don’t need to do this
but adherents claim 100 percent success rate.

Using warm laps and warm water for cutting and polishing is strongly
recommended. This warning is probably irrelevant for any cutters using their living space. The advice was offered because of problems a cutting shop encountered on Monday mornings after a cold weekend. Room temperature laps and water is the goal.

Heavy flushing during cutting and polishing is also strongly recommended

Accomplishing the entire cutting process as quickly as possible is highly
recommended. Leaving a half completed stone for another day’s session is
warned against.

Annealing.
I don’t know the source but I believe Farouq assigned it to Marc
Liccini. The suggestion is that brittle tourmaline can be annealed in a
toaster oven. 450F is the temperature that will change the colour or
saturation so it would probably be wise to stay below that. I have never
tried annealing tourmaline but the suggestion is that an annealed stone
has fewer untoward cutting characteristics and doesn’t require as much
special care and attention. No experience, no comment.

Tony.