CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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PostPosted: Tue Jul 31, 2007 10:00 pm 
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Essentially, I am arguing that the color variety "ruby" is an idiochromatic gemstone, i.e., a color variety of the allochromatic mineral corundum which must contain chromium in order to qualify as a ruby.


May I begin by saying that this discussion would be best suited around a kitchen table with a bottle of red wine. (Which is where most of my meaningful discussions take place) :wink:


We can split additional hairs here.
Can this chromium bearing red corundum contain iron and still be considered a ruby?
Is the genesis of the formation a consideration for identification? Roland Schuussel would argue that conditions under which red corundum is formed is the ULTIMATE criteria for determining ruby vs. red(dish) sapphire.

I think this argument really revolves around how much mineralogy one chooses to study in order to understand gems. A "GEMOLOGIST" can adequately get by memorizing that rubies are red varieties of sapphires. For most, this will suffice.

Is ruby idiochromatic? In my (never so humble) opinion,
no.
Chromium percentage? Iron percentage? Gallium? Beryllium diffusion? Genesis?


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PostPosted: Wed Aug 01, 2007 1:06 am 
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Philosophy is just a metaphor for thinking. Whether you're considered a cynic or philosopher depends solely on your audience.


And I think one could also say that what is considered relevant or irrelevant is also dependent on the audience, no?


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PostPosted: Wed Aug 01, 2007 1:29 am 
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Barbra Voltaire wrote:
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Philosophy is just a metaphor for thinking. Whether you're considered a cynic or philosopher depends solely on your audience.


And I think one could also say that what is considered relevant or irrelevant is also dependent on the audience, no?


LOL


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PostPosted: Wed Aug 01, 2007 3:49 am 
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OK, now you have done it--made me use my brain and actually study.

In my (not so professional) opinion, I believe that everyone has over complicated this whole issue.

First of all sapphire is not a gem species, it is a variety of corundum, and corundum is allochromatic because in its pure state it is colorless. Ruby is a red variety of corundum just as emerald is a green variety of beryl. It is interesting that chromium is an allochromatic coloring agent of both ruby and emerald.

Peridot is idiochromatic because it contains iron, no iron-no peridot.

Mr. Hanneman, I understand your proposal, but I must respectively disagree. Too much of gemology is intertwined with mineralogy and different definitions for the same words would, I believe, cause only more confusion. I understand why you would say that Ruby is an idochromatic gemstone, as it must contain chromium to to be called a Ruby, but a Ruby is still a variety of corundum.

I really do hope that I have not overstepped any boundaries with my response and if any of my information is incorrect please tell me. I am honestly trying to grasp all of these concepts and at this point my brain hurts. :smt120

Roberta


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PostPosted: Wed Aug 01, 2007 9:31 am 
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I think you did just fine, Roberta :D .

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PostPosted: Wed Aug 01, 2007 9:57 am 
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Barbra Voltaire wrote:
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Philosophy is just a metaphor for thinking. Whether you're considered a cynic or philosopher depends solely on your audience.


And I think one could also say that what is considered relevant or irrelevant is also dependent on the audience, no?


Touche Barbra!

Oh, and Jason, I think along with your gem specimens for sale you should include information as to which are allochromatic and which are idiochromatic.

It's not relevant to me, but, it may be to others. :)


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PostPosted: Wed Aug 01, 2007 9:59 am 
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I really do hope that I have not overstepped any boundaries with my response and if any of my information is incorrect please tell me. I am honestly trying to grasp all of these concepts and at this point my brain hurts.


There are no boundaries on this forum when it comes to a good discussion! I think your presentation is a good one (as I happen to agree with it cough cough :wink:).


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PostPosted: Wed Aug 01, 2007 10:17 am 
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Hi,

I like thinking about these things, especially when my mind wanders in all directions.
Agreed it is of lesser importance, unless you are asked to explain it and some smart bugger comes up with some impossible questions. Trust me, happened to me many times.

Bill,

I took sapphire as an example and created the formula for simplicity.
As a gemmologist I'm trained that sapphire without a prefix is always blue, the same as "a brilliant" which always refers to diamond.

Of course the chemical composition of (blue) sapphire is not (Ti,Fe)Al2O3, there are many other elements in it. But lets say for the discussion it contains only those 4 elements. Now the corundum formula does not apply anymore.
I was thinking from that angle about it.


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PostPosted: Wed Aug 01, 2007 11:37 pm 
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Barbra

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May I begin by saying that this discussion would be best suited around a kitchen table with a bottle of red wine. (Which is where most of my meaningful discussions take place)

You will have to leave me out. Red wine gives me a headache. However, in the spirit of the occasion let me say that I am not really trying to convince anyone of anything—just give you something to think about. I respect that each of you is entitled to your own erroneous beliefs.:lol: :lol:

Quote:
We can split additional hairs here.
Can this chromium bearing red corundum contain iron and still be considered a ruby?

If it is red, it has to be.

Quote:
Is the genesis of the formation a consideration for identification? Roland Schuussel would argue that conditions under which red corundum is formed is the ULTIMATE criteria for determining ruby vs. red(dish) sapphire.

The conditions under which any mineral is formed is the ultimate criterion for determining its composition. (time, temperature, ions available, phase equilibrium etc.)
Ruby — red sapphire. That is a distinction made only to increase the perceived value of a “poorly colored” ruby. You will notice no one has attempted to define the “dividing line.” It is a question, the answer to which depends on whether one is buying or selling.

Quote:
I think this argument really revolves around how much mineralogy one chooses to study in order to understand gems. A "GEMOLOGIST" can adequately get by memorizing that rubies are red varieties of sapphires. For most, this will suffice.

Quite possibly, but he would be wrong, and that is not saying much for what you expect from gemologists, or else it is an admission that mineralogical nomenclature is irrelevant to gemology—a point with which I might not argue too much. However, ruby can’t be a variety of sapphire, as the two are, by mineralogical nomenclature, mutually exclusive mineral varieties (of corundum).
Quote:
Is ruby idiochromatic? In my (never so humble) opinion, no.
Chromium percentage? Iron percentage? Gallium? Beryllium diffusion? Genesis?

Check the definition of the adjective “idiochromatic.” It says nothing about composition. To the public, the noun “mineral” has a different connotation from the noun “gemstone.”
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RAR.
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I understand why you would say that Ruby is an idiochromatic gemstone, as it must contain chromium to to be called a Ruby, but a Ruby is still a variety of corundum.

And a man and a woman are varieties of humans, but one can’t call a man a woman, for obvious reasons. Likewise, one can’t call a ruby a sapphire for obvious reasons.

But Barbra argues ruby is a variety of sapphire. I doubt if the public cares. To the public, ruby is simply a red stone with a hardness of 9—next to diamond.
--------------------------------
Doos
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As a gemmologist I'm trained that sapphire without a prefix is always blue,

And when a customer asks a jeweler or a trained gemologist, “Will you please show me some fine sapphires,” should he bring out only blue stones or also some yellow, orange, and green stones? Or should he ask if there is any specific color he would like to see?


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PostPosted: Thu Aug 02, 2007 12:33 am 
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Hi guys:

I'm confused (so whats new) but I thought that one of the definitions of ruby was that it contained chromium or vanadium. so if this is true then true rubies that are lighter in colour are still rubies and not "red" sapphires.

If sapphires do come in red then what is the colouring agent?

Thanks

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PostPosted: Thu Aug 02, 2007 12:50 am 
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A lot of sellers term beryllium diffused red corundum "red sapphire", especially material from Songea. It is usually a very highly saturated red, specifically, medium dark, moderately strong orangy red.

The stones can be really pretty, with a very velvety texture.


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PostPosted: Thu Aug 02, 2007 12:57 am 
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Hi Barbra:

Thanks barbra ... are all songea sapphires pretty much Be treated?

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PostPosted: Thu Aug 02, 2007 1:23 am 
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Dr. Hanneman wrote:
Check the definition of the adjective “idiochromatic.” It says nothing about composition.


I disagree (as usual :wink: ). An idiochromatic mineral is one where the coloring agent is essential to its chemical composition.

I have also heard it suggested that the streak of allochromatic minerals is white, while that of idiochromatic minerals is colored.

That may be the case with minerals like malachite, hematite and azurite, but I've never seen a green streak left by peridot, Ah Ha! :idea: Perhaps proof that peridot is REALLY just a variety of allochromatic forsterite....

Wolf wrote:
are all songea sapphires pretty much Be treated?

All the RED ones that I've seen have been. The ones listed on eBay are listed as "heated" but I would bet if you sent the owners a PM they might say that the stones could have been diffused as well.


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PostPosted: Thu Aug 02, 2007 2:36 am 
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Only at the Rock-E Horror Gem-O-Rama, would I expect to have males and females confused, likewise, Ruby and Sapphire. I would never go there anyway!

Why would anyone buy a gemstone from someone who could not tell the difference? :-s


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PostPosted: Thu Aug 02, 2007 10:26 am 
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Why would anyone buy a gemstone from someone who could not tell the difference?


It's cheap


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