Do Emeralds change color under "blacklights"?

[soberguy]

Fluorescence

Another test to determine synthetics from natural emeralds is exposing it to Ultraviolet radiation (or UV rays). Synthetic emeralds transmit UV light more than natural emeralds.
There are two common ultra-violet rays used for fluorescence. Those are short wave and long wave rays. Short-wave rays are ones with smaller wavelengths but with lighter frequencies and power in terms of penetration to the gemstone. Exposed to short-wave rays emeralds may show reddish fluorescence and when exposed to long-wave rays neutral fluorescence.

Alternatively the Chelsea Filter (an apparatus used by gemologists through which when an Emerald is viewed it appears red due to its chrome content) may be used to determine specific red fluorescence under short wave.

Consumers should also beware of fluorite and chrome Diopside, which are very close imitations of emeralds when set in jewellery.

References:


http://www.jewelinfo4u.com/Emerald_Identification.aspx

 

[serenitydiamonds]

That's not a really good source. The Chelsea filter separates visible light, not SW UV.

http://en.wikipedia.org/wiki/Chelsea_filter

--Joshua

 

[chrono]

The Chelsea filter is mainly to detect the presence of chromium, not to check for fluorescence, isn’t it? Or more specifically, it is not meant to separate long wave and short wave reaction.

 

[serenitydiamonds]

The Chelsea filter is mainly to detect the presence of chromium, not to check for fluorescence, isn’t it? Or more specifically, it is not meant to separate long wave and short wave reaction.

That's correct.

--Joshua

 

[soberguy]

I called GIA, and they said natural emeralds, especially in "fine colors" CAN fluoresce orange to red in LW and SW UV light...

 

[RockHugger]

It's in my gemstone ID book. The finer the color, the more chromium is present. Thus the fluor. As long as it's not lit up like a candle, it is ok. Bright red glow needs more testing (inclusions, sg, ect) to know of it's natural.

And the local makeup is in there too. Muzo mines are usually colored by more vanadium then chromium. They usually have a slight yellowish green hue to them, along with bluish glow. Fluor is less common in them.

Chivor mine emeralds have more chromium and less if no vanadium, giving them a bluish green hue. It also gives them fluor.

 

[chrono]

I do not recall where I read this but chromium coloured emeralds are only found in Colombia and that it is this same high chromium content that causes the frequent inclusions seen in these emeralds because the larger chromium atoms causes greater stress on the crystal structure, forming fissures, similar in the way that chromium affects fine quality Burmese rubes. The vanadium bearing emeralds are only from Africa which tends to be cleaner because of this.

 

[RockHugger]

Chivor and muzo mines are in Colombia. Vanadium is found in Colombian emeralds as well. I think chromium is only found in Colombia.

 

[LD]

The presence of Chromium in most gems acts as a fluorescer (so I would conclude Emeralds are not different).

The presence of Vanadium does not

The presence of Iron actively acts to cancel out fluorescence.

So, if you have an Emerald with any amounts of the above, it MUST depend on the ratio of each as to whether fluorescence is evident or not. What I am reading (and also confirming with my home-made experiments ) is that IF an Emerald fluoresces, it only shows weak fluorescence and not strong or red (like an Alexandrite or Ruby) - this seems to be a generic agreement on the web.

Interestingly, if you throw into the equation that some treatments may cause fluoresence as Joshua has indicated you have a very confusing picture and one that I believe can't be determined by normal gem buyers and needs further investigation with specialist lab equipment.

 

[LD]

Fluorescence

Another test to determine synthetics from natural emeralds is exposing it to Ultraviolet radiation (or UV rays). Synthetic emeralds transmit UV light more than natural emeralds.
There are two common ultra-violet rays used for fluorescence. Those are short wave and long wave rays. Short-wave rays are ones with smaller wavelengths but with lighter frequencies and power in terms of penetration to the gemstone. Exposed to short-wave rays emeralds may show reddish fluorescence and when exposed to long-wave rays neutral fluorescence.

Alternatively the Chelsea Filter (an apparatus used by gemologists through which when an Emerald is viewed it appears red due to its chrome content) may be used to determine specific red fluorescence under short wave.

Consumers should also beware of fluorite and chrome Diopside, which are very close imitations of emeralds when set in jewellery.

References:


http://www.jewelinfo4u.com/Emerald_Identification.aspx

SG I read this article also but didn't post it up because there were a number of inaccuracies in the article that completely contradicted more reliable sources. I don't know them so can't be positive but I'm not sure I'd rely on this article too much.

 

[serenitydiamonds]

I guess we'll just agree to disagree. I called GIA and spoke to the lab, and she read the same paragraph from the book to me that she probably read to you. It's rare, can fluoresce red or orange, and found typically only in fine stones.

In my experience of thousands of emerald parcels of super fine quality Colombian emeralds, I haven't seen one natural emerald fluoresce under UV light. I use UV light to identity and grade treatments. Treatments and fillings typically respond to UV light. I'd be willing to show a parcel of super fine gems in UV light with no reaction if you'd like verification of my experience.

Super fine gems can, and most typically do, fluoresce red in bright visible light.

Perhaps there are some rare cases that respond with light fluorescence. I know that if I came across one, I'd send it to the lab for confirmation.

There's a fabulous article in Sep 2009 of Rapaport on what impurities are present in which particular emeralds. I strongly suggest reading it to get the facts correctly. I have a digital copy if anyone would like to borrow it to read.

--Joshua

 

[chrono]

http://www.geo.utexas.edu/courses/347k/redesign/gem_notes/Beryl/beryl_triple_frame.htm

I don’t know how accurate this is but many things are puzzling:
1. Here, it claims the Chivor is bluer green (cool) and the Muzo is yellower green (warm)
2. Can distinguish between Chivor and Muzo origin by lower SG and RI
3. Zambian material is bluer green than Colombian!
4. Fluorescence – confirms that it will be weak if present.

Thank you to Josh for calling GIA to confirm/clarify the issue of fluorescence in emeralds.

 

[T L]

Chrono,
To point 3, Zambians being bluer than Colombian, not from what I've seen. I think Colombian emeralds have a lot of blue in them. Zambians remind me more of tsavorites in color. People can feel free to disagree with me.

 

[soberguy]

I think I was the one to call GIA... lol!

 

[LD]

I think I was the one to call GIA... lol!

Both you and Joshua did but your posts slightly contradict each other I think!!!

At the end of the day, if you're worried about your Emerald then I think it's best to send to a Lab because there's so much differing of opinion that it would be wise to do so.

 

[LD]

Chrono,
To point 3, Zambians being bluer than Colombian, not from what I've seen. I think Colombian emeralds have a lot of blue in them. Zambians remind me more of tsavorites in color. People can feel free to disagree with me.

They remind me of Chrome Diopside! I don't generally like either!

Much prefer the vividness and velvetyness of a gorgeous blue/green Emerald from whatever location but I have to say I've never seen a Zambian I personally like!

 

[T L]

I've never seen a Zambian I personally like!

LD,
I have not either . Might as well get a tsavorite instead, because to me emeralds are about their glowy velvet luster and their fine saturated slightly bluish green color.

 

[RockHugger]

I have a Zambian emerald and it's a very deep green, and very very clean. But it doesn't have the glow my colombians have.it's just...green. Like others said, like a chrome diopside.

 

[Nick_G]

This is a really od thread, so apologies for bumping it up from the grave, but it appears that some emeralds do indeed fluoresce red under LWUV. This is a specimen from the Panjshir Valley in Afghanistan that I pulled the trigger on today:


Now I don't have this specimen in my hands yet, and it'll probably take 2-3 weeks to reach me as it's coming from a seller in Pakistan, but that fluorescence looks quite amazing in the pics. Logically those emeralds must be high in chromium with no iron.

I'll certainly update this thread when the specimen arrives, and take some pics.

 

[Nick_G]

The emerald specimen above arrived today. Gorgeous crystals and of course photos can't do the intensity of the green justice. It's almost like the metallic green of a mallard duck if that makes any sense. And yes those crystals really do fluoresce a very obvious red in my LWUV torch. I've never seen any emerald fluoresce like that .

I'll take some better pics tomorrow, but here's a poor one showing the UV fluorescence:

 

[Nick_G]

Here are some pics of the emerald specimen:


Of course, the camera cannot really do justice to the intense saturated green of those emerald crystals.