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 Post subject: parti-/bi-colour vs uneven colour zoning
PostPosted: Sun Oct 23, 2005 8:49 pm 
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In another thread, Martin wrote "parti colour or bi colour, is a bit different then uneven colour zoning" . Martin, could you or someone explain the difference to me? I thought I understood the difference but on another forum I was told I was wrong so I would like help on this.


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PostPosted: Sun Oct 23, 2005 9:10 pm 
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Parti-colour, means “make motley”, or “has different colours”. So it infers the stone will have more than one colour. Good example of these are the Australian parti-colour stones, that are shown in another thread. These commonly blue / yellow / green varieties are referred to as parti-coloured. (But the term does not infer a particular colour – these are just common in Australia, but not the only variations.) These almost always have a cheaper pcp than evenly saturated stones of a single colour.

Bi-colour technically means two colours.

Colour zoning is the effect seen in non evenly saturated stones, which is usually not a desirable attribute. Much rough has colour zoning, that can often be eliminated by proper orientation during cutting, although when you flip the stone upside down, you will see the zones clearly as paler or clear streaks or bands. They usually only detract significantly from the value if the are visible face up. GIA grading for instance is done face up, so technically, you could buy a stone that is fairly heavily zoned, with a good grading, if the zoning is not visible face up.

Does this make sense?

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PostPosted: Sun Oct 23, 2005 10:59 pm 
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Thank you, Martin. Those definitions are pretty much as I understood them to be, which makes me feel that my comment about a photo on the other forum had been correct and I had been told I was wrong. That photo is no longer available or I would bring it up for discussion. If/when I come up with a photo similar, I will post it to continue my question. I know I don't have anything similar in my own collection. :|


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PostPosted: Sun Oct 23, 2005 11:06 pm 
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You know what my dad always said Gemma? "People are entitled to their opinions, but that doesn't change the facts”…

; -)

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PostPosted: Mon Oct 24, 2005 5:09 am 
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Hello,

In the following inclusion photos you can see stones with color zoning:
Heated Palin Sapphire:
Image
Unheated Pailin sapphire:
Image

Now looking as these stones from Ambondromifehy (north madagascar) you will see some stone which are one aera completly yellow while the rest is blue:
Image

A zebra has color zoning, a panda bear is more bicolor... for some cows well it is more complicated... LOL

All the best,

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The views expressed here are V. Pardieu’s opinions and do not necessarily reflect those of GIA Laboratory Bangkok (http://www.giathai.net)where he is an employee since Dec 2008.


Last edited by vincent pardieu on Tue Mar 04, 2008 5:08 pm, edited 1 time in total.

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PostPosted: Mon Oct 24, 2005 7:54 am 
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And a calico cat is parti-coloured? :D

Good way to put it Vincent, that makes it totally clear.


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PostPosted: Mon Oct 24, 2005 9:00 am 
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Thank you, Vincent. Then I believe now I was correct in thinking the stone was zoned. (PS: I like your animal analogies; very easy to remember differences now. :) )


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PostPosted: Mon Oct 24, 2005 10:53 am 
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The image links for Vincent's post were not working properly, so I corrected them.
These are EXCELLENT pics and shouldn't be missed :!:


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PostPosted: Mon Oct 24, 2005 1:09 pm 
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Thanks Barbra,
I hope I will be able to do it myself next time... What was wrong?
All the best,

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The views expressed here are V. Pardieu’s opinions and do not necessarily reflect those of GIA Laboratory Bangkok (http://www.giathai.net)where he is an employee since Dec 2008.


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PostPosted: Mon Oct 24, 2005 2:56 pm 
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The html code got all mucked up. :?
I removed the bits that didn't belong in it, and voila....worked like a charm :P


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PostPosted: Wed Oct 26, 2005 11:34 pm 
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Nice one there Vincent!
That sure is something easy to remember!
Zebra = colour zoning
Panda = bi-colour


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