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 Post subject: Gem Quiz
PostPosted: Mon Jul 24, 2006 6:47 pm 
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This is a good portion of the face up view of this gem in darkfield lighting.

Identify the gem AND describe why it looks this way.

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PostPosted: Mon Jul 24, 2006 7:09 pm 
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My first though is rain in a flux ruby. Intersections at 120 degrees.

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PostPosted: Mon Jul 24, 2006 7:25 pm 
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This is the stone in late afternoon natural roomlight.



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PostPosted: Tue Jul 25, 2006 6:45 pm 
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No other guesses eh? Can't say I blame you.

Doos gets at least partial credit, it is corundum. Although natural.
I have several pieces of this low quality material, each exhibits some interesting growth features.

Being translucent they don't make very good photo subjects as some of these features are so faint they just don't show up in enough detail to be visually helpful in the images.

The quiz stone tested as corundum. 1.76 approx. spot reading.It showed two fluorescent chromium lines in the red around 690, as well as general absorption in the yellow and most of the green. It has a weak to moderate red reaction to LWUV, inert to SW.

As you can see it is reddish purple with purple being the more dominant in normal light.

As for the appearance in the first image....I was hoping someone here could explain. It appears to have distinct color banding in one direction as well as distinct color zoning running at an oriented angle to the banding.
Don't know if this occured simultaneously or if it represents an interruption in growth and then new growth in a different crystal orientation.

Anyone here want to venture an opinion?
I've searched the www trying to find any similar images without luck.


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PostPosted: Tue Jul 25, 2006 11:37 pm 
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There is a similar sapphire photo in the color plates of Matlin's Gem ID Made Easy. The caption say it's silk with needles intersecting at 60 degrees. Can't offer any more than that . . . :oops:


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PostPosted: Thu Jul 27, 2006 11:55 am 
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I see fishy dye-like colour on the background...
Fishy colour banding from top to bottom...
Polysynthetic twinning from left to right...

that's what i see.....wrong? :?


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PostPosted: Thu Jul 27, 2006 1:26 pm 
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OK, Riniel, you made me look at it more closely and so, no, it doesn't look like the photo in GemIDME. Hmm, is that a dyed surface?


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PostPosted: Thu Jul 27, 2006 1:57 pm 
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Dying could be a suspicion, but the broad patches of color are one directional. I have no reason to believe dye is involved. This stone is double cabbed both sides being rounded like a somewhat flattened jelly bean.

The pattern you see repeats itself on the flip side.

A more complete view of the stone in darkfield.

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PostPosted: Thu Jul 27, 2006 4:45 pm 
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Are you sure it isn't a jelly bean with swirls of undissolved sugar? :shock:


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PostPosted: Thu Jul 27, 2006 5:12 pm 
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Nope, tastes just like corundum to me.

btw: I gave it good bath in acetone...cleaned it nicely with no change in appearance,or evidence of dye.


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PostPosted: Thu Jul 27, 2006 6:02 pm 
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OK, if one sees the same thing on both sides and it is double cabbed, then is it a doublet and what you are seeing is the adhesive?


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PostPosted: Thu Jul 27, 2006 6:31 pm 
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No, No, this isn't any kind of trick question. It is corundum and not an assembled stone of any sort.

I'm just trying to get a definitive answer on the banding and zoning(?).

The cause and relationship if any.

Just a learning exercise for us. :)


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PostPosted: Thu Jul 27, 2006 10:39 pm 
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OK, I saw in Photoatlas of Inclusions I in the Corundum section many photos and references discussing the zone effect in Burma and Sri Lanka stones. And the photos look similar there too. Does that sound plausible? But I don't think that explains the "banding", though I could look a little closer at the atlas if you think this is the right track.

Modo, it looks like a used Ricola cherry cough drop to me!


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PostPosted: Fri Jul 28, 2006 6:21 pm 
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I think if Riniel can catch Vincent in a slow moment, he may have some insight.

Anyone that looks at corundum on a daily basis, in various locations and a wide range of quality has probably seen similar characteristics before.

Just need them properly defined.

This isn't jewelry quality stuff, just material that's telling a story and I don't know the ending yet.


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PostPosted: Fri Jul 28, 2006 10:33 pm 
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I think Vincent is still on his trip...he should back soon...
maybe he'll visit this page when he gets back....


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