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 Post subject: Turmalin
PostPosted: Mon Jun 18, 2018 12:04 am 
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Joined: Wed Jun 02, 2010 2:46 am
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ich habe das problem, das beim schleifen von grünen turmalin sprünge entstehen. das turmaline unter spannung stehen ist mir bekannt. hat jemand eine lösung diese steine zu entspannen?


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 Post subject: Re: Turmalin
PostPosted: Mon Jun 18, 2018 2:37 am 
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Location: Cape Town, South Africa
nonprofana wrote:
ich habe das problem, das beim schleifen von grünen turmalin sprünge entstehen. das turmaline unter spannung stehen ist mir bekannt. hat jemand eine lösung diese steine zu entspannen?

"I have a problem when cutting green tourmaline that cracks develop. I know that tourmaline is under stress. Has anyone a solution to relax these stones?"

Some tourmaline crystals have short cracks in the rind and if you grind this rind off first, before dopping and cutting the stone, these cracks don't travel further into the stone. Unfortunately some tourmalines simply continue cracking, usually at right angles to the length of the crystal. This is particularly the case with dark green stones, but I have had it happen with blue-green Nambian stones too. As far as I know there is no solution to this problem.


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 Post subject: Re: Turmalin
PostPosted: Mon Jun 18, 2018 1:12 pm 
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Location: Vancouver, Canada
The only advice I have is that if you have tourmaline that has or develops cracks when cutting, is to cut as fast as possible to remove the crack so it doesn't propagate further. However, even when you eliminate the crack it is possible for the stone to spontaneously crack later after being completed.

Unfortunately some tourmaline are highly-stressed and have suicidal tendencies. I find that blue tourmaline tend to be the worst - Afghan and Nigerian have caused me grief in past.

Good luck!

-Allan

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 Post subject: Re: Turmalin
PostPosted: Mon Jun 18, 2018 8:33 pm 
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Joined: Mon Aug 20, 2012 11:32 pm
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Location: Florida, United States
I recommend two procedures:
1. Tap each crystal lightly with a wood or plastic mallet.
This procedure breaks up the most strained areas into less strained, facetable pieces.
2. Preform each piece using a wheel with diamond grit range no coarser than 28-40 micron.
This procedure prevents propagation of cracks into the stones.

Und auf Deutsch:

Ich empfehle zwei Verfahren:
1. Klopfen Sie jeden Kristall mit einem Holz- oder Plastikhammer leicht an.
Bei diesem Verfahren werden die am stärksten beanspruchten Bereiche in weniger beanspruchte, facettierbare Teile aufgeteilt.
2. Preform jedes Stück mit einem Rad mit Diamantkornbereich nicht grösser als 28-40 Mikron.
Dieses Verfahren verhindert die Ausbreitung von Rissen in die Steine.

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 Post subject: Re: Turmalin
PostPosted: Wed Jun 20, 2018 10:56 am 
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The link below provides some valuable insight and recommendations. It was posted by Tony the Gem DR, some years ago and helped me a lot.
http://www.thegemdoctor.com/wp/2010/01/ ... procedure/

Personally I remove any striations by hand on a 600 lap always in the direction of the striations.
Avoid any thermal shock.
Do not use any lap coarser than 600 grit
Only attach to dop once the stone is cleaned up.

Regret my German is not good enough to translate.


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 Post subject: Re: Turmalin
PostPosted: Wed Jun 20, 2018 10:48 pm 
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Joined: Wed Jun 02, 2010 2:46 am
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vielen Dank für die Antworten


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