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 Post subject: Help in identifying a stone
PostPosted: Wed Nov 03, 2021 2:08 am 
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Hi all! I am trying to identify a purple stone, but have no equipment with me. It does not scratch with the tungsten pen, yet it is not sapphire as there are no doubling of facets. It is an old cut emerald cut, this has less facets than today's cuts. It weighs in at 2 CT and measures 7.98 mm x 6.14mm x 3.92 mm. It is a transparent stone, it has no identifiable inclusions except maybe for some crystal like inclusions/abrasions on the cut cornered girdle. It also tests positive for a diamond on a diamond tester. My question are the following: what does tungsten scratch? There is no doubling of facets, so it's not a moissanite. I keep thinking that the measurements and weight say it a sapphire, but I see no doubling of facets. Please , what am I doing wrong? Thanks


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 Post subject: Re: Help in identifying a stone
PostPosted: Wed Nov 03, 2021 12:07 pm 
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The birefringence of sapphire is very low. Before looking for doubling of the back facets, I'd check for dichroism.


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 Post subject: Re: Help in identifying a stone
PostPosted: Wed Nov 03, 2021 12:36 pm 
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What a predicament. Follow the experts advice given first.
What is the importance of old Emerald cut verse new if I may ask. Emerald cut is an Emerald cut, many of styles have irritated over the years. Are the tier levels straight and parallel to each other or is it traditional cut stone bulging Pavillion and uneven facet lines?

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 Post subject: Re: Help in identifying a stone
PostPosted: Wed Nov 03, 2021 9:00 pm 
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Hi thanks. I have more info on the stone. I may have posted this separately. I'm new to this, and have trouble finding what I have posted. First of all, this is a purple stone, it is bright red under the Chelsea filter, and has green fluorescence under uv light. I don't have any instruments with me. My measurements are not accurate as other measure 4.16 depth. Thanks all


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 Post subject: Re: Help in identifying a stone
PostPosted: Wed Nov 03, 2021 11:27 pm 
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Post a picture of the stone, please.
The information you are providing is not very useful.


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 Post subject: Re: Help in identifying a stone
PostPosted: Thu Nov 04, 2021 1:30 am 
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I was travelling so I just carried a few things, so I don't have any more information. The only scientific information is purple color, bright red under Chelsea, green to olive green under uv. Harder than tungsten scriber. The pic is under uv. It was not dark inside, because it was not my stone nor my house to do as I please. I do not own the stone, nor can I do any more tests on it.


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 Post subject: Re: Help in identifying a stone
PostPosted: Thu Nov 04, 2021 1:01 pm 
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Could you possibly just take a picture of the stone? No UV, no Chelsea Filter, just the stone.
Thanks.


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 Post subject: Re: Help in identifying a stone
PostPosted: Thu Nov 04, 2021 1:19 pm 
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Edited: removed content as it duplicated what Barbra just asked.

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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 3:07 am 
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The pictures I took were not great. I posted the blurriest photo because I wanted to ask that I remember on this forum many years ago, someone posted that there was a method of gem identification or maybe it being about sorting rubies from other gems, without any instruments by looking at the refraction of the light, by holding the stone very close to the eye and looking at a light source. Maybe I'm totally wrong on why this was used, but I think I'm correct on the method.


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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 6:51 pm 
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Aptemerald wrote:
it was not my stone

Woahhh, just as a general note you really shouldn't do hardness tests on cut stones, but especially not on cut stones you do not own. Not only is scratching a potential problem (of course) but putting that kind of pressure on a stone can also cause it to cleave or break. Sure it's not super probable but improbable things tend to happen at the worst times.

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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 7:20 pm 
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Quote:
I wanted to ask that I remember on this forum many years ago, someone posted that there was a method of gem identification or maybe it being about sorting rubies from other gems, without any instruments by looking at the refraction of the light, by holding the stone very close to the eye and looking at a light source. Maybe I'm totally wrong on why this was used, but I think I'm correct on the method.


https://gemologyonline.com/Hanneman_Guide.html

It is a link in the menu bar to the left

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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 7:40 pm 
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With both eyes open, and no candles involved, I'd guess it's vanadium doped synthetic sapphire, with a color shift depending on light source,


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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 7:40 pm 
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Sorry guys, this one is all yours...


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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 8:24 pm 
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This method was originally developed by Alan Hodgekinson. Dr Hanneman does a good job explaining it here:
viewtopic.php?t=3424

Several years ago, I hosted a Gem Nerd dinner party with Alan Hodgekinson and his wife. After dinner, and an essential pour of a dram of highland single malt for all, we turned off the overhead electric lights and left the candles burning to use as our light source for VO. It was a total success and by the end of the evening we were doing some impressive identifications using our eyeballs as refractometers.

A bit of a backstory. When Alan was a young inspired and aspiring, unemployed gemmo, he made a living driving taxis in Glasgow. One rainy night, waiting for a fare which never arrived, using the beam from an overhead sodium street light and holding the ring he was wearing up to his eye, he saw what appeared to be the spectrum of the stone. As all inspired gemmologists have on hand, in one pocket or another, he brought out several unmounted gems and started viewing them in the same way. Visual Optics was born that night.


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 Post subject: Re: Help in identifying a stone
PostPosted: Fri Nov 05, 2021 8:33 pm 
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Barbra that is a nice memory.

Do you happen to know how many (NB) posts have been made with this same scenario of a purple stone, green under UV. Being called a color change sapphire. Seems like a lot.

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