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 Post subject: Scottish Beryl question
PostPosted: Sat Nov 25, 2017 3:11 pm 
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Hi Folks, I don't know whether I've come to right place or not but let's see.
I am an amateur mineral/gem collector and I found six examples of what I believed to be Beryl in the Cairngorms in Scotland this summer. Beryl is present here but it is extremely rare and people can spend a lifetime looking and never find it. It has taken me countless trips over 20yrs but eventually, I got lucky.
Now then, I thought one of my six might have been good enough to cut & polish so I took it to the Scottish Lapidary & Mineral Club in Edinburgh and they kindly, successfully managed to turn it into a cabouchon and also set it in in a handcrafted Silver pendant for my wife's birthday. Apparently, it is the only Beryl Aquamarine that they have ever cut from Scotland; they have 100 members & have been going for nearly 50 years. Going some then.
However, once it has now been set and finished and the present was given, the stone appears to change colour depending on whether it is in daylight or artificial light. Outside, it is distinctly blueish and indoors it turns to a more greenish colour. This has got me thinking whether it may actually be a Chrysoberyl and not Beryl Aquamarine; as I cannot find any reference to Aquamarine changing colour?
Can you help me determine whether it is or isn't one or the other - how can I actually identify what it is?

Many thanks
Tony


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 Post subject: Re: Scottish Beryl question
PostPosted: Sun Nov 26, 2017 2:50 am 
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Some shift wouldn't be too atypical for a green-blue aquamarine. It definitely has a very berylly look. I don't think chrysoberyl would be much of a possibility. Good work finding one! I have heard of beryl and, if I remember right, topaz from the area, but never seen an example.

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 Post subject: Re: Scottish Beryl question
PostPosted: Sun Nov 26, 2017 6:14 am 
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I have heard from a mineralogist friend last night that Beryl although rarely, can display this property. Also, because the stone took a polish from cerium oxide - that was another indicator that it isn't a Chrysoberyl. Must try harder!
Yes Topaz is found here too but they are even rarer than the Beryl, I visited another collector in the summer and held in my hand the Topaz he found - it was the size of a small orange and mostly blue throughout. I'll be looking for Topaz next summer. Actually I have been looking for it for many years but probably in the wrong location; now I know which mountain does hold them I can narrow my search.


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 Post subject: Re: Scottish Beryl question
PostPosted: Sun Nov 26, 2017 2:43 pm 
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BritishMinerology.com wrote:
Beryl

Beryl is a silicate mineral of beryllium and aluminium, with the chemical formula Be3Al2Si6O18 and is very much less common in the Cairngorms than smoky quartz, but significantly more abundant than topaz. Well-crystallised, beryl forms distinctive hexagonal prismatic crystals, with flat (pinacoidal) terminations. It is slightly harder than quartz and has a similar specific gravity (2.76, compared to 2.65 for quartz).

Beryl is of widespread occurrence in the Cairngorms, generally as waxy yellow-green prismatic crystals up to a few centimetres in length, enclosed in granite, but also as disseminations in granite, and as distinct well-formed crystals in quartz. Exceptionally, beryl occurs as gem-quality, transparent colourless, blue, yellow-green or green prismatic crystals.
Quote:
Image
Deeply corroded, transparent, gem-quality crystal of beryl. Beinn a’ Bhuird. Photo Copyright © Roy Starkey 2014


Many of the beryl crystals recovered from the Cairngorms are deeply etched and corroded as a result of the action of highly corrosive late stage fluids. Such fluids, sometimes including high concentrations of hydrogen fluoride which is required to form topaz, may alter beryl to phenakite or bertrandite, and rarely to genthelvite, all of which have been reported from the Cairngorms.


Read More about minerals in the Cairngorms


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 Post subject: Re: Scottish Beryl question
PostPosted: Sun Nov 26, 2017 4:24 pm 
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:D I have Roy's book too; he and I have discussed the Cairngorms Beryl and Smokey Quartz locations at some length, neither of us have managed the ultimate prize of the Topaz yet.. but we'll keep trying!


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 Post subject: Re: Scottish Beryl question
PostPosted: Tue Aug 17, 2021 1:07 am 
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I received an email from Andy Moffat,
Andy Moffat wrote:
Please inform Tony 'Fastmarlindriver' that the cabouchon he has had cut and polished from the Cairngorms, is not beryl or chrysoberyl but is in fact a typical example of Cairngorms polycrystalline topaz.

Image

viewtopic.php?f=37&t=24116


Probably from Ben Avon or more likely Cairngorm? Also, rarely found on Beinn Mheadoin

A very lucky find.

Best wishes.

Andy Moffat


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 Post subject: Re: Scottish Beryl question
PostPosted: Thu Aug 19, 2021 1:25 pm 
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That's interesting, but the stone in question doesn't look especially polycrystalline to the eye. Usually polycrystalline topaz is white and opaque but the ones I'm vaguely familiar with are not scottish and from a pretty different geological environment.
I'd love to give it a quick raman scan but it having been four years I doubt the OP is still checking in.
If it is an unusual topaz I'd love to have a sample for my topaz collection.

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 Post subject: Re: Scottish Beryl question
PostPosted: Fri Mar 18, 2022 3:11 pm 
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Just randomly visited and saw the reference to the stone possibly being Topaz. I can definitely say it was not a Topaz. It wasn't 'heavy enough' to begin with - Topaz has a higher SG than Beryl and I have handled many Topaz crystals for years (buying & selling). Secondly, it changed colour between natural sunlight and indoors artificial light; although this is rare in Beryl; I have found no reference for any Topaz to perform this colour change.

The stone was not found on Ben Avon or Cairngorm - I found it on Beinn a' Bhuird.

I know where a big Scottish Topaz was found (not Beinn a' Bhuird) and I hope to find one myself soon; I'll begin looking as soon as the snows have melted this year.


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 Post subject: Re: Scottish Beryl question
PostPosted: Fri Mar 18, 2022 10:02 pm 
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Have you thought of taking a refractive index on the specimen, along with SG?
Doesn't look like topaz to me either.

Who is the mineralogist. Maybe I know them. I was a member of the Scottish Gemmological Society for many years. :)


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