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 Post subject: Oiled emeralds: how to remove the oil?
PostPosted: Fri Dec 07, 2012 6:28 am 
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Greetings all

Can anyone advise on how to remove the oil from emeralds? Any advise on this subject would be greatly appreciated. Thank you in anticipation.


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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Fri Dec 07, 2012 12:17 pm 
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Immersion in oil solvent like The Acetone

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Tue Dec 11, 2012 5:50 am 
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Thank you roshanravan

How effectively does this remove the oil? Is it enough to expose the major fractures commonly found in some of the Zambian goods?


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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Tue Dec 11, 2012 1:16 pm 
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Yes Acetone is first choice for removing oil from Emerald. :D :D

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Tue Dec 11, 2012 3:54 pm 
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I dunno but I've been told: Once oiled it is impossible to get all the oil out, meaning lab report of none can't be achieved. Why would you do that? If you just want to see how heavily it has been oiled - there is easier methods.

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Tue Dec 11, 2012 6:28 pm 
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If you do not have acetone available or it does not remove all the oil, try soaking the emeralds in hot ethyl alcohol, occasionally stirring the alcohol.

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Wed Dec 12, 2012 12:29 am 
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Wouldn't you be able to remove all the oil by doing repeat extractions with vacuum cycling and hot acetone?


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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Wed Dec 12, 2012 1:45 am 
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Thank you all for your time and fantastic advises.

@mikko. What are the easier methods of identifying how much oil is used. Magnification can indicate whether the goods have been oiled or not. But, how can we determine the extent of it? :?

@Arya. What exactly is vaccum cycling? :oops:

I'm getting my hands on some acetone today. Will immerse the emeralds. Any advise on how long i need to keep them immersed?

Truly greatful to you all for your input.

Regards


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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Wed Dec 12, 2012 4:24 am 
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Quote:
@mikko. What are the easier methods of identifying how much oil is used. Magnification can indicate whether the goods have been oiled or not. But, how can we determine the extent of it?


My favorite method is fluorescence microscopy.
Most oils fluoresce green when illuminated with 405 nm (non-collimated!!!!) laser pointer. Additionally, a color filter blocking both blue 405 nm (for safety) and red chromium fluorescence of emerald is required. When only green color is allowed to transmit in to microscope the oil shows up as green network inside the stone.

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Wed Dec 12, 2012 11:10 am 
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shoaibmotiwala wrote:
@Arya. What exactly is vaccum cycling? :oops:

Basically you apply a vacuum, drawing out some of the oil. Then you swirl the solution around and release the vacuum. This forces acetone into the space that formerly had oil. That helps the deeper oil dissolve. Repeat this process several times. Its like the reverse of the process used to impregnate cracks with oil.


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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Thu Dec 13, 2012 9:56 am 
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mikko wrote:
When only green color is allowed to transmit in to microscope the oil shows up as green network inside the stone.


You don´t happen to have a picture or two of that?

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Thu Dec 13, 2012 2:33 pm 
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Sorry, my current microscope camera is lousy, can't capture faint fluorescence good enough. This is really the application where differences between cameras become most obvious. While reaction can be easily seen with human eye the camera needs chilling and prolonged exposure times. I'll try to arrange some pics next time when I have access to proper gear.

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Thu Dec 13, 2012 7:18 pm 
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Quote:
hot acetone

DON'T DO IT!!

Hot acetone will very easily ignite and EXPLODE.

Acetone fumes will explode if not carefully ventilated.

Please take extreme care if you attempt this. Electric sparks from vacuum pumps may be enough to cause a fire or worse.

-Allan

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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Thu Dec 13, 2012 10:00 pm 
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gembug wrote:
Quote:
hot acetone

DON'T DO IT!!

Hot acetone will very easily ignite and EXPLODE.

Acetone fumes will explode if not carefully ventilated.

Please take extreme care if you attempt this. Electric sparks from vacuum pumps may be enough to cause a fire or worse.

-Allan

CRAP sorry, forgot that this was going to be done at home and not in a chem lab!


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 Post subject: Re: Oiled emeralds: how to remove the oil?
PostPosted: Fri Dec 14, 2012 12:56 am 
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gembug wrote:
Quote:
hot acetone

DON'T DO IT!!


Having first hand experience I must second that!

I was working at semiconductor lab early nineteens. Doing nothing wrong but strictly following the process manual I was cleaning photoresist from silicon wafers with hot acetone. It was early R&D phase and there was not yet wet bench for acetone. The manual instructed heating 5 liters of acetone to the boiling point in large glass beaker on hot plate. Suddenly the acetone boiled out and when reached the hot plate it ignited. We tried to reach the fire blanket but only after 5 seconds the halon system of the cleanroom was triggered. That was not quite pleasant experience but saved the lab. Total cost of the incident was however $$$$$ because halon system did not get refilling license and had to be replaced with more environmentally friendly system.

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