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 Post subject: brownish, grayish or greenish deviation in diamond color
PostPosted: Fri Mar 11, 2011 5:47 am 
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many years ago I've bought a diamond with GIA certificate the color was graded as "I" but it has a brownish deviation and made the stone very light brown. surprisingly it was also cheaper than other similar color/clarity/cut but it was unsatisfying color so i had to return it to the vendor. that was when i understood the color grading for colorless to light yellow diamond is according how white and yellow the diamond is regardless of color deviation.
the color deviation might effect color origin for example exceptional white colors (D,E,F) with grayish deviation in industry they call silver or faint brownish in some colors they call rose. some of these faint deviation might look good and many effect the appearance and not satisfying, your diamond is graded white but you see unsatisfying light brown or gay subcolor in it. i would like to know if there is any more articles/references about it and color deviation effect on different color grades

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sat Mar 12, 2011 10:28 pm 
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Great question....I have no idea, sorry.
I know the eye sees brown more than yellow. I have never seen grey color (or have not realized it). The color grade is determined by some esoteric combination of tone and hue...(or some such thing); not just tone alone, which could possibly be realized with some sort of filter to simulate total color blindness.
It has been a long while since I read my diamond grading manual.
Mostly I wanted you to have a response to your query. Sorry it's not more precise.


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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Mar 13, 2011 1:15 am 
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Thank you Richard i know how to grade colors,
-colorless to light yellow diamonds (D-Z)
-colored diamond darker than light yellow or equivalent or with another noticeable hues or tones

the thing i wanna know is more articles on effect of brownish, grayish or greenish deviation in colorless to light yellow diamonds. and trade names guideline for brownish/grayish/greenish colorless to light yellow diamonds.

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Mar 13, 2011 5:42 am 
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for example some grayish colorless and near colorless diamonds will exhibit a metallic hues and mirror sharp brightness and sometimes its not a pleasurable color, Sometimes the pink or blue appears as a slight tinge in grayish and exhibit pink metallic or blue metallic. also with enough brownish in Light Yellow diamonds might result color like Olive or Light Champagne. but grayish in light yellow is not satisfying color like brownish in colorless/near colorless.
i am looking for more information about this subject. if any exists. (or i am the only one who finds this interesting)

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Mar 13, 2011 10:33 am 
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It sounds as though you have seen many more diamonds than myself. The only modifying colors (other than fancy colors like blue, pink, green etc) I have seen are brownish modifying colors. Perhaps someone out there will know of articles discussing the phenomenon you are describing.


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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Jul 03, 2011 3:54 am 
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I did some research that i thought i should share with GO, it could be useful for others.

First some facts from GEMS & GEMOLOGY WINTER 2008 - COLOR GRADING “D-TO-Z” DIAMONDS:
the normal color grading for colorless to yellow diamond as we all know is from D to Z but Color Grading Brown or Gray Diamonds has different masterstone set

Quote:
Color Grading Brown or Gray Diamonds in the D-to- Z System. From its inception, the D-to-Z system included near-colorless to light brown diamonds. Prior to and throughout the 1980s, the use of yellow master stones for brown diamond comparisons was a common procedure. At that time, the brown diamonds typically submitted for grading reports were in the E-to-J range. While there is a noticeable difference in hue, brown diamonds in this range share tone and saturation qualities with their yellow counterparts (for a discussion on the three attributes of color—hue, tone, and saturation—see King et al., 1994). This made the visual comparison to yellow masters compatible for brown diamonds in these letter grades. With the influx of stones from Australia’s Argyle mine since the mid-1980s, there has been greater industry awareness and marketing of brown diamonds (Richardson, 1991). As a result, more brown diamonds have been submitted to the GIA Laboratory, not only in the near-colorless region but throughout the color grade scale. Accordingly, the laboratory created a master set of brown diamonds (figure 20). As these stones become darker, the differences in hue, tone, and saturation are more pronounced. This contributed early on to the laboratory’s decision to begin associating a word description with the letter grades of brown diamonds beginning at K (figure 21). Today, a letter grade plus word descriptions of “Faint brown,” “Very Light brown,” and “Light brown” are used for the grade ranges of K–M, N–R, and S–Z, respectively.


Quote:
The color transition between brown and yellow diamonds is continuous, and the laboratory occasionally encounters diamonds with color appearances that are “in-between” the two different colors of the master sets (e.g., yellow-brown). It is important to choose the appropriate set of masters (i.e., yellow or brown) for the comparison process. This is usually accomplished by comparing the diamond being graded to both sets and selecting the one closest in appearance. We recognize that others in the industry do not have D-to-Z scale brown master sets (and grading brown master stones is not a service the GIA Laboratory currently offers). Assessing the color of brown diamonds using only yellow master stones can be challenging. When doing so, the observer must remember to assess the overall depth of color— the combined effect of tone (lightness to darkness) and saturation (strength or weakness) of a color (King et al., 1994). Some observers try to grade just as they would yellow diamonds, and only look for saturation differences (the “amount” of yellow), which can result in an incorrectly high determination compared to laboratory grading. If yellow master stones are the only ones available, the observer should assess the overall depth of color and equate it to the overall depth of the yellow master stone. The reporting approach for gray diamonds is similar to—but not the same as—that used for browns. In the colorless to near-colorless range (E to J), they are graded using the D-to-Z scale letter grades. Beginning at K, though, gray diamonds receive a word description only of “Faint,” “Very Light,” or “Light” gray for the same letter grade ranges as for brown diamonds (King et al., 1994). Although gray diamonds are reported with only word terms in this range, historically they have not been considered a “fancy” color until they reach a description of “Fancy Light” (as with yellows and browns). Color Grading at the Lower End of the D-to-Z ange. Color grading at the lower end of the scale (below N or O) can present special challenges for graders. As the color becomes more noticeable, so do the differences between color attributes. In determining the relationship of a diamond to a master stone, an observer must contend with subtle differences in tone (lightness or darkness) and hue (as opposed to the predominance of saturation in the decision making for other areas of the scale). The difficulty in making grade distinctions between single color grades in this range limits the usefulness of all the individual color grades in theO-to-Z range. More important, we have found that such fine distinctions are not in demand among the laboratory’s clients; nor are they significantly useful to the trade for valuing these diamonds. We have informed clients that reporting color grades in this portion of the grading scale by using grade ranges is the best solution. The master stone locations used for laboratory reporting, are O, Q, S, U, W, Y, and the Z/Fancy Light boundary. Therefore, GIA grading reports will note a color as “S–T range” or Y–Z range,”


GIA Color Grade Terminology Boundaries:
Attachment:
color-grade-terminology-boundaries.png
color-grade-terminology-boundaries.png [ 57.48 KiB | Viewed 4332 times ]


GIA Brown MasterStones Comparing with yellow masters:
Attachment:
GIA-BrownMasterStones-Comparing with yellow masters.png
GIA-BrownMasterStones-Comparing with yellow masters.png [ 41.75 KiB | Viewed 4332 times ]


also i managed to get two diamond with GIA Certificate which both are Z color but in both Yellow and Brown boundaries which approves the color grading system:
Attachment:
YZ.png
YZ.png [ 36.66 KiB | Viewed 4332 times ]


there could be four type of color modifier, we already know Brownish and Grayish modifier that GIA system explained, but there are also Whitish modifier which results in milky color diamonds (not good luster and too much milky make Fancy white) and greenish modifier which i think is kind of mixture of brown and yellow in lower color grades, (plus some metallic modifiers)
its still on going research for myself and due lack of stones to test i can not write more but if i get any more details i will share here,

i think fluorescence has also effect on the color modifier. in levels of
Negligible/Faint/Moderate/Strong with (powder effect or not) in Blue/GreenishBlue,Yellow,Green,Red/Orange,White (all diamond's fluorescence colors) but still i need to do more tests, i would be glad if you guys share your experience with me.

i am also checking with other LABs and it seems there is no clear picture. the HRD system says:
Quote:
diamonds can be divided into three large groups - diamonds with a yellow color hue, diamonds with a brown/gray color hue and diamonds with a different color hue. This can be schematically represented as demonstrated below. Only the diamonds falling in the shaded zones can be called "fancy."

Image
courtesy of am-diamonds


unfortunately nothing about the color modifier on other Labs
please note that these kind of colors are very rare but they exist.

Also note the Argyle Color system for Brown Diamonds:
Quote:
The Champagne Diamond Color Scale
C1 ("Light Champagne") : N,O,P,Q colors
C2 ("Light Champagne") : R,S,T,U,V colors
C3 ("Medium Champagne") : W,X colors
C4 ("Medium Champagne") : Y,Z colors
C5 ("Dark Champagne") : Fancy Brown
C6 ("Dark Champagne") : Fancy Brown to Fancy Dark Brown
C7 ("Fancy Cognac") : Fancy Dark Brown

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Last edited by roshanravan on Sun Jul 03, 2011 7:51 am, edited 2 times in total.

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Jul 03, 2011 6:11 am 
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My theory why we are lacking what you ask for, is that most of these stones used to become industrial diamonds. Not long ago, 15 yrs or so, one could in the industrial diamond trade find very nice stones with, for the jewelry trade, "unwanted hues". Today on the other hand it seems all kinds of stones are cut for jewelry. I see cut stones today wich I would have regarded as rejects when sorting rough under my time in the cutting industry.
"Fancy white" would have been considered a joke.

In short: IMHO the problem might be that the trade is not yet updated.

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Jul 03, 2011 7:01 am 
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Conny Forsberg wrote:
My theory why we are lacking what you ask for, is that most of these stones used to become industrial diamonds. Not long ago, 15 yrs or so, one could in the industrial diamond trade find very nice stones with, for the jewelry trade, "unwanted hues". Today on the other hand it seems all kinds of stones are cut for jewelry. I see cut stones today wich I would have regarded as rejects when sorting rough under my time in the cutting industry.
"Fancy white" would have been considered a joke.

In short: IMHO the problem might be that the trade is not yet updated.

these colors already exist in trade and there is supply and demand for it, the problem is there is not enough clarification from Labs, specially from G~J Colors (not mentioning there is nothing said about greenish/milky/metalic modifiers

The Argyle mine is major producer of Brownish Diamonds and i have seen Metalic-pinkish color modifier in some high color diamonds from Brazil (actually very satisfying color) so when there is nothing said in science the trade can not get update (although trade uses these terms)

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Sun Jul 03, 2011 9:13 am 
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Which I did not contradict in my statement...

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Mon Jun 04, 2012 10:36 am 
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just an update regarding Grayish color deviation in diamonds. i thought it might be useful some day for some one :wink:

True gray diamonds are assigned color grades on a scale of light (smoke) gray to dark (graphite) gray, but gray most often appears as a secondary color in green or blue diamonds.

Gray diamonds have not historically been a popular choice for jewelry, but in winter of 2009-2010, mining giant Rio Tinto – which owns the Argyle diamond mine – rolled out a line of silvery-gray diamonds called Silvermist, which were priced at 20%-40% less than comparable-quality colorless diamonds. Silvermist are 2% of Argyle mine's colored diamonds.

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 Post subject: Re: brownish, grayish or greenish deviation in diamond color
PostPosted: Mon Jun 04, 2012 10:49 am 
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The so called Silver colored diamonds have been around for a long time. Which I actually have called gray since I first saw one. Never seen the Argyle stuff you mention though.

I think it is a great way of marketing diamonds of lower value that might be regarded nice and attractive by some market segment. Also the comparably lower price could be regarded attractive. I guess here in Scandinavia people are a bit too conservative to make this a big sales item around here.

Still I do question the habit of some dealers to market completely milky, clouded diamonds as "white" :)

Thanks for the info Ros.

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