CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: What is used to harden soft gemstones?
PostPosted: Sun Dec 30, 2012 11:27 am 
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For treating soft and brittle gemstones such as sphene with some kind of transparent lacquer/enamel/varnish kind of coating to increase the hardness and durability of these stones?
I am sure that there must be something out there that could be effectively used to treat softer gemstones. Is there any such thing?


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 Post subject: Re: What is used to harden soft gemstones?
PostPosted: Sun Dec 30, 2012 2:16 pm 
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DionysusGem wrote:
For treating soft and brittle gemstones such as sphene with some kind of transparent lacquer/enamel/varnish kind of coating to increase the hardness and durability of these stones?
I am sure that there must be something out there that could be effectively used to treat softer gemstones. Is there any such thing?
DionysusGem,
Sorry to bear bad news.... in the past 32 years in the gem trade, I've not learned of any substance that was/is used as a durability enhancement.

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 Post subject: Re: What is used to harden soft gemstones?
PostPosted: Sun Dec 30, 2012 3:56 pm 
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In the late 60´s they had a treatment going where they steamed on a protectiv layer of Quartz on different soft gemstones(Chudoba-Gübelin Edelsteinkundliches Handbuch Page 320) the problem was that the gemstone(host) must have similar structure-analogie to the coating otherwise the coating would not bind.

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Last edited by earthling on Sun Dec 30, 2012 4:08 pm, edited 1 time in total.

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 Post subject: Re: What is used to harden soft gemstones?
PostPosted: Sun Dec 30, 2012 4:03 pm 
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Well.... memory is coming back, apparently!

There is a firm known as Azotic Coatings in Minnesota. They have been placing coatings on all types of substances including sunglasses, prescription glasses and numerous other uses. It is possible to use their techniques on gemstones as they have been treating Topaz with various colors for some time.

I would surmise they do not perform 'one-offs'.

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 Post subject: Re: What is used to harden soft gemstones?
PostPosted: Tue Jan 01, 2013 9:10 pm 
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I guess soft stones can be coated with thin DLC films or thin synthetic CVD/PVD polycrystalline diamond films.

steatite is slightly hardened through heat treatment.


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 Post subject: Re: What is used to harden soft gemstones?
PostPosted: Tue Jan 01, 2013 11:37 pm 
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ROGER DERY wrote:
There is a firm known as Azotic Coatings in Minnesota. They have been placing coatings on all types of substances including sunglasses, prescription glasses and numerous other uses. It is possible to use their techniques on gemstones as they have been treating Topaz with various colors for some time.

Roger, I think Azotic coatings are used to change gems' color, not harden them. Topaz (8 hardness) which receives the most Azotic treatments probably doesn't need hardening anyhow. Azotic colored coatings are usually applied to the pavilions of stones like "mystic topaz" to create a plethora of other unnatural and strange topaz hues.

Someone mentioned Opticon. It's been around for at least half a century and is used as a fracture-filler, not a stone-hardener per se. Major uses I'm aware of are for filling gaps and fractures in quartz minerals and especially heavily-fractured gems like Brazilian emeralds, both rough and cut, and occasionally to repair crazed opals.

It and other epoxy resins are used for lots of other things as well, including pressure infusing into soft, porous turquoise "chalk" and perhaps other porous materials. That last use might considered a method of "hardening" but the end result is still pretty soft.

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 Post subject: Re: What is used to harden soft gemstones?
PostPosted: Thu Jan 03, 2013 4:17 pm 
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ROM wrote:
Someone mentioned Opticon


Rick, I was asking about Opticon but deleted my posting afterwards because some google research revealed it's not used for hardenig, so I felt my question was off-topic here.

Thanks for your explanation anyway!

The correct trading name for this substance seems to be Opticon 224.

best regards,
Michael


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