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 Post subject: Re: Emerald Grading
PostPosted: Sun Sep 13, 2015 8:47 am 
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Location: Cape Town S.Africa
Hi Farshid
Thanks for that.Unfortunately,my customer for a large number of emeralds
insists on no treatment at all[except for cutting,of course].He will have them
all certified and needs a "no oil" result.I want to make sure they pass this test
with no problems.I am sure they have had no treatment,but it may be that some
oil was used during cutting,so I want to make sure that is removed,if present.
So I intend to "de-oil" even the crystal specimens,just in case there is a small
amount of oil on the surface.There are about 2000cts and,if unoiled emerald is
as rare as "hen's teeth",as it appears,there is a great incentive to get "clean"
certification.These are also Sandawana emeralds,which,in themselves,are rated
very highly,the smaller stones being particularly beautifully coloured and mostly
with no cracks.Even in the 1980's,the very small ones[<0.2ct] were selling for
over $500 per ct as they hold their colour down to even the smallest few pointers.
As such,they are perfect for melee used to highlight diamonds etc.
The mine closed down some years ago and these stones originate from artisanal
miners.I have seen some rough parcels and they have no oil smell and I cannot
imagine they would have access to cedarwood oil,etc.Unfortunately,the cutter has
died,so I cannot check with him.
Thank you for all your feedback-it is much appreciated.


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 Post subject: Re: Emerald Grading
PostPosted: Sun Sep 13, 2015 9:55 am 
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raygem wrote:
Hi Farshid
Thanks for that.Unfortunately,my customer for a large number of emeralds
insists on no treatment at all[except for cutting,of course].He will have them
all certified and needs a "no oil" result.I want to make sure they pass this test
with no problems.I am sure they have had no treatment,but it may be that some
oil was used during cutting,so I want to make sure that is removed,if present.
So I intend to "de-oil" even the crystal specimens,just in case there is a small
amount of oil on the surface.There are about 2000cts and,if unoiled emerald is
as rare as "hen's teeth",as it appears,there is a great incentive to get "clean"
certification.These are also Sandawana emeralds,which,in themselves,are rated
very highly,the smaller stones being particularly beautifully coloured and mostly
with no cracks.Even in the 1980's,the very small ones[<0.2ct] were selling for
over $500 per ct as they hold their colour down to even the smallest few pointers.
As such,they are perfect for melee used to highlight diamonds etc.
The mine closed down some years ago and these stones originate from artisanal
miners.I have seen some rough parcels and they have no oil smell and I cannot
imagine they would have access to cedarwood oil,etc.Unfortunately,the cutter has
died,so I cannot check with him.
Thank you for all your feedback-it is much appreciated.

then in that case its better to consult with some labs, as you said yourself GGTL Lab in Liechtenstein they have de-oiling service and they might do parcels for better price. but 2000cts gonna cost a fortune to get report!

best of luck, maybe later you share your experience and costs. it might come handy for others

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http://diamondclub.us
Blog: http://roshanravan.tumblr.com/


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 Post subject: Re: Emerald Grading
PostPosted: Sun Sep 13, 2015 10:17 am 
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Location: Wylie Texas but in Alaska for a while
It sounds like you have some amazing material. Any chance of some pictures for those of us who can only drool over something like a 2000 emerald?


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 Post subject: Re: Emerald Grading
PostPosted: Sun Sep 13, 2015 10:52 am 
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Joined: Wed Oct 17, 2012 12:20 pm
Posts: 108
Location: Cape Town S.Africa
Hi Wilson.It isn't a 2000ct emerald-wish it was-but a lot of smaller emeralds.
Would post pictures if I knew how.I have taken some with my ipad as is,
also with the iPad placed on one of the microscope eyepieces,but they are
not of the quality one finds on this site.If you send me an e-mail,I can send
you some pics as I don't know how to load them onto this site.
I got a grading set made up by EGL[by sending in stones that I thought were
of poor to good quality].So I have gradings for colour,clarity,brilliance for sets
of emerald,aquamarine,demantoid,tanzanite,tourmaline and a few others,I think.
It helps me a lot as they are real stones for me to use as grading comparisons.
Maybe not so good on the computer images,but if you are interested,I can e-mail
them to you.
EGL uses the ICSL system developed by a real helpful guy,Ian Campbell.Sadly,he died
recently.RIP.
Cheers
Ray


Last edited by raygem on Sun Sep 13, 2015 11:23 am, edited 2 times in total.

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 Post subject: Re: Emerald Grading
PostPosted: Sun Sep 13, 2015 11:07 am 
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Joined: Wed Oct 17, 2012 12:20 pm
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Location: Cape Town S.Africa
Thanks Farshid-my customer will get the certificates done before he puts them on his site.
I will take back any that get an "oiled" result but,as they are all from the same source,
it is probably a matter of all oiled or all unoiled.I am holding my breath waiting for the
results for the first parcel.I did put some in methylated spirits for a few days with regular
agitation and I could see no difference under the microscope.I am doing some more now-
I have pics before Meths,will take pics again after meths,then steep in acetone and then
in HCl or oxalic acid and take pics at each stage.
Cheers
Ray
PS-I would use hydrofluoric acid,but don't have enough life insurance.
As they say in the Classics-"People in glass houses shouldn't throw hydrofluoric acid" !!!


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 Post subject: Re: Emerald Grading
PostPosted: Mon Sep 14, 2015 4:33 am 
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Location: Cape Town, South Africa
raygem wrote:
I would use hydrofluoric acid
On emerald?!! :shock:


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 Post subject: Re: Emerald Grading
PostPosted: Mon Sep 14, 2015 4:46 am 
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Location: Cape Town S.Africa
Duncan
I see your point!!!


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 Post subject: Re: Emerald Grading
PostPosted: Mon Sep 14, 2015 11:30 am 
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Location: San Francisco
raygem wrote:
Hi Wilson.It isn't a 2000ct emerald-wish it was-but a lot of smaller emeralds.
Would post pictures if I knew how.I have taken some with my ipad as is,
also with the iPad placed on one of the microscope eyepieces,but they are
not of the quality one finds on this site.If you send me an e-mail,I can send
you some pics as I don't know how to load them onto this site.

Cheers
Ray

Hi Ray....
The first link on the left, after the GemologyProject graphic is entitled
How to Post Pictures on the Forum

If you can't sort it out, send some pics to me and I'll get them up for you. :D
bav@gemologyonline.com


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 Post subject: Re: Emerald Grading
PostPosted: Mon Sep 14, 2015 11:39 am 
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Location: Cape Town S.Africa
Thanks Barbra


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 Post subject: Re: Emerald Grading
PostPosted: Tue Sep 15, 2015 11:10 am 
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Location: Cape Town S.Africa
I have just had a good laugh to myself.Checking the prices for emerald
gem reports,the price for an untreated specimen is more than for an
enhanced specimen.
But I then realised it made good sense.It is obviously more difficult to
prove a negative than a positive.


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 Post subject: Re: Emerald Grading
PostPosted: Tue Sep 15, 2015 1:25 pm 
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Unless your client has had a chain of custody from the miner on, there can be no guarantee that the rough has not been oiled. I submitted an emerald to AGL a while back and the report came back stating they found evidence of light oiling. As I provided the rough directly to the cutter, who used no oil in the process, I called them and asked how that could be. They told me that they could offer no explanation other than the testing procedure they used was very sensitive and would indicate even faint traces of oil if present. The only conclusion I can arrive at is that the rough was oiled before I purchased it. I purchased the rough over 25 years ago and the dealer has long since passed.

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 Post subject: Re: Emerald Grading
PostPosted: Wed Sep 16, 2015 3:15 am 
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allen wrote:
Unless your client has had a chain of custody from the miner on, there can be no guarantee that the rough has not been oiled. I submitted an emerald to AGL a while back and the report came back stating they found evidence of light oiling. As I provided the rough directly to the cutter, who used no oil in the process, I called them and asked how that could be. They told me that they could offer no explanation other than the testing procedure they used was very sensitive and would indicate even faint traces of oil if present. The only conclusion I can arrive at is that the rough was oiled before I purchased it. I purchased the rough over 25 years ago and the dealer has long since passed.


roshanravan wrote:
for your information, since sixteenth century when Spanish conquistadors brought emeralds from the Chivor and Muzo mines in Colombia, after mining and polishing they would have kept emeralds in oil for transportation to prevent abrasion & scratching themselves. traders still use this method for transportation as it is the safest way for emerald for transportation. but still there are some goods that has not been oiled after polishing which traders mostly do that for very high quality products and in that case soon after polishing they get lab report to prove that, this is not common for poor to good quality ones.


i am again quoting myself, no one can vouch for using no oil in the process unless the rough from the mine to polishing is handed On a silver platter all the way :lol:

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http://diamondclub.us
Blog: http://roshanravan.tumblr.com/


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 Post subject: Re: Emerald Grading
PostPosted: Wed Sep 16, 2015 4:01 am 
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Allen and Farshid-Thanks for that info.I have started soaking my
samples in methylated spirits[USA Benzine?] until I get some acetone.
That way,I will know the lab. won't find any oil,but,if there is Opticon
or similar there,they should find that.As far as I know,Opticon etc is not
available in Zimbabwe.It is difficult to even get cutting/polishing abrasive,
so I am pretty sure they will be "clean" after soaking.Microscopy showed
no difference before and after soaking.If anything,appearance seemed to
improve slightly,probably because any dirt,polishing dust etc was removed.


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 Post subject: Re: Emerald Grading
PostPosted: Thu Sep 17, 2015 12:50 pm 
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Sorry, try 3 typo The author.... sent me some photos of the stones he was talking about. I am posting them for him. He recently posted some wonderful pictures in the off the dop thread, so I hope that we can see more of the close- ups in the future.


Image

Image

Image

Image


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 Post subject: Re: Emerald Grading
PostPosted: Mon Sep 21, 2015 3:41 am 
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Location: Cape Town S.Africa
For interest,on the emerald gading sets above,the ICSL system
letters stand for in descending order].
C=Colour
B=Brilliance
C=Clarity
F=Final Grade
The ICSL system is very punitive-great for buyers,less so for sellers!!
For a size indication,the stone on the left is 4.2ct.


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