New Mineral Named After GIA’s John Koivula
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 Post subject: Burmese, origin description or indicator of quality in ruby?
PostPosted: Thu Jul 18, 2019 11:51 am 
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I open the few emails that I get with something interesting in them and found this.

Gem Guide, Gem Focus July 2019 - featuring ruby.

The article starts with the following assertion.

"The classic Burmese stones have set the quality standards for Rubies for centuries."

This statement of origin does not really work well with the inability of gemological knowledge/science to even distinguish red gems such as tourmaline, spinel and corundum from each other, centuries ago, let alone determine where they came from. So how did "Burmese" become associated with top quality Rubies for centuries? Yes, Burma does produce top quality Rubies and probably dominated their production. This fact along with a long history of production and the lack of gemological knowledge, lead the trade to distinguish top quality Ruby as "Burmese" rather than having it denote its origin. This state of affairs was explicitly stated in Schuster's Guide to Gems and Precious Stones, a classic sources of information about gems and one of my favorite books growing up. (An updated and revised edition still makes the same contention.)

Yes the world moves on and the abilities of the gemological laboratories have certainly changed the gem world. Still history should not be forgotten or rewritten and the great outrage some declared against naming some cuprian tourmaline from locations other Paraiba Brazil, paraiba, lacks a reasonable historic perspective. The effort should be considered in light of the need to convey the quality of a gemstone to a potential buyer. With no references for the glow-like qualities of some cuprian tourmaline, except high quality Paraiba tourmaline, paraiba is not an unreasonable name for all cuprian tourmaline that make the grade. Like all high quality Rubies use to be referred to as Burmese in the good old days.

As always these are my opinions.

Bruce


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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Thu Jul 18, 2019 12:56 pm 
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I haven't had the opportunity to read the Gemguide article yet. Some of these topics were probably covered in it.

The only source of ruby, for centuries, was the Mogok stone track in Burma.
Therefore, it is logical to presume that all other sources would be compared to the original source.

The fact that other stones were misidentified as ruby doesn't change that.

If I may quote from the Dr James Shigley:
Dr. James Shigley wrote:
Rubies of Burmese origin have long been considered the finest quality in the world. The mines in the area called the Mogok Stone Tract in north-central Burma have been known to produce the most important rubies, and reports of rubies from this area have been made by explorers and other travelers since the time of Marco Polo. The Mogok area, along with other parts of the country, came under control of the British in late 1886, when investigations of the geological setting of the ruby occurrence began and gem mining became more organized.

If you would like to puruse historical texts on ruby, there is a list here.
https://www.gia.edu/ruby-mines-burma-reading-list

Some of the rubies discovered in the Mogok area of Burma have the supernatural quality of being so fluorescent they glow in sunlight.
Anne Sasso in the Geology of Rubies wrote:
That remarkable radiance—caused by any ultraviolet light, including UV rays from the sun—has given rubies a special place in history. Long before Marco Polo found his way to Asia, Burmese warriors were embedding the stones under their skin to make them invincible in battle. Sanskrit medical texts were prescribing rubies as a cure for flatulence and biliousness. And Hindu lore was preaching that a ruby’s light could not be extinguished nor hidden by clothing. Geologists can explain the glow: Ultraviolet light causes the chromium in rubies to fluoresce. But there is much about rubies that scientists cannot account for. The biggest question, the one that has geologists on both sides of the Atlantic at odds with each other, is how rubies formed in the first place. Geologists simply do not know. That rubies even exist, says Peter Heaney, geosciences professor at Penn State University, is something of a “minor geological miracle.”
READ MORE


Dick Hughes wrote:
Ruby's red glow is like the snowflake and the rainbow. In one of those glorious accidents of nature, ruby is blessed with both a red body color and a tendency to take bits of visible blue and green light and blast them back with a laser-like red emission. Indeed, the first lasers made use of this very property (synthetic ruby is still a common laser material).
READ MORE


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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Fri Jul 19, 2019 10:57 am 
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Fascinating info Barbra - thanks for the links.

I didn't realise there was such speculation around rubies.
(But then I'm only a 3 year part time newbie... lots to learn)

Interestingly I've been looking into the source of a few things the last few
weeks - there's Fe60 and Al26 both of which are
believed to have supernova origins.
While I don't know of either being inclusions of anything (and Al26
wouldn't be too nice) - it is interesting that both Fe and Al are
related to corrundum (with the Fe being of note due to peculiar absence if I understand
correctly)

I'm not suggesting a connection - just a coincidence with my current reading.
But I do need to read more on rubies prompted by yourself and Bruce.


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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Mon Jul 22, 2019 10:41 am 
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hi johngemmo

Aluminum is a fundamental building block of corundum... corundum's chemical form is Al2O3.

Chromium is a trace impurity in corundum that gives ruby its red color and red fluorescence... some Cr3+ ions replace Al3+ ions in the corundum crystal.

Iron Fe3+ is a trace impurity in corundum that gives a slightly different red color, but does not cause ruby to fluoresce. In fact, iron reduces any red fluorescence that may be present via chromium.


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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Tue Jul 23, 2019 4:31 pm 
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Thanks for the info Brian -

Quote:
Iron Fe3+ is a trace impurity in corundum that gives a slightly different red color, but does not cause ruby to fluoresce. In fact, iron reduces any red fluorescence that may be present via chromium.


So would I be right in thinking a lack of flourescence in a ruby isnt necessarily a contra-indicator for ruby?
My favourite pocket reference book - (the Schumann 'gems of the world') has ruby flourescence listed
as "strong: carmine" The book does mention iron (in terms of colour change to more brownish hues) but doesn't mention flourescence in this respect so this is good (and useful) info for me.

When I get round to buying in some ruby I guess I can do some comparisons but it's nice to have the info for what to look for.


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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Tue Jul 23, 2019 4:33 pm 
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Right. Iron quenches ruby fluorescence. Thai rubies have a reputation for it. They can still be fine and valuable gems.

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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Wed Jul 24, 2019 11:52 am 
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Yep, as you say, iron concentration can be so high as to effectively kill fluorescence.

If I was in the field looking for ruby, I'd use one of those compact 405 nm flashlights to illuminate samples... that wavelength produces brighter fluorescence than the traditional LWUV lamp. If I saw no evidence of fluorescence in a sample, I'd use a dichroscope to eliminate garnet and spinel as possibilities. But I'd still worry about it until I checked its RI.

If I was really serious, I would just use a Raman like Stephen. :)


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 Post subject: Re: Burmese, origin description or indicator of quality in r
PostPosted: Thu Jul 25, 2019 8:51 am 
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Thanks - guys

Yes I was planning to use a raman like (or from) stephen last year but unforseen personal
events took over and forced me to change everything I'm doing.

Going back to a website I used for reading on flourescence in saphires I see it does discuss this
for rubies aswell - I guess it must have just fallen out of what passes for my memory.

If anyone is interested the link is:
http://www.ruby-sapphire.com/heat_seeker_uv_fluorescence.htm
The web site is worth a look if it's new to you. I've found it quite instructive.


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