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Color code for a citrine


#1

Can anyone tell me what the “color master code” used by the
Gemological Laboratories in Los Angeles in 1981 was? I know little
about gems and need some help on this.

A customer wants a replacement for a large citrine and she gave me a
description and appraisal of the original that contains a description
of the color in terms of the “color master code”. I have seen the
original (which has been stolen), and my memory is that it was a pale
yellow, but when one looks into it, it viewing it through the thickest
part, is indeed a very attractive honey color, and the facets around
the side reflect ambient light quite beautifully.

I have never seen a citrine with the same color characteristics. All
the large ones I have seen are significantly darker, and I have
assumed this is due to the fact that they are produced by heat
treating. The customer does not like the large dark colored citrines
she has seen, and wants to get a new one of the same color as the old
one. The appraisal has the following description, including a
description of the color in terms of a "color master code:

	Shape: Mixed oval Step Cut
	Length: 26.05 mm
	Width:  20.53 mm
	Depth:  12.9  mm
	Weight:  46.38 Cts.
	Florescence (1w) inert
	     "      (sw) inert

Cut: Fair, large window in center of stone. Polish: Poor, abraded
crown and pavilian facet junctions, polishing marks, surface scratches
and abrasions.

	Phenomena: None
	Inclusions: no visible inclusions under 10X magnification
	Color master code: OB, 33, 77, 04
	Color: Medium light yellow
	Clarity: Internally Flawless
	Comments:  None
	Conclusion:  Natural Citrine Quartz.

dian


#2
    Can anyone tell me what the "color master code" used by the
Gemological Laboratories in Los Angeles in 1981 was?  I know little
about gems and need some help on this. 

Dian, as no one else has jumped in on this question, I’ll tell you
what little I know about it.

The ColorMaster was a machine introduced by the GIA which was used to
"dial in" the color of a stone. You would adjust the amount of Red,
Blue, and Green light along with a “modifier” to try to duplicate
the color of a stone you had in hand. There was also a shape selector
which allowed you to show a round, oval, emerald, etc cut on the
screen. It was a difficult machine to use and in my opinion, the GIA
was right in dropping it from their classes. You can simulate it
today by using some of the drawing programs on your PC and using the
custom colors editor, set values for each of the color segments.

As to what the Color master code: OB, 33, 77, 04 means, it is an
Orange/Brown color, the 33 is the setting on the red, 77 is the
green, and 04 is the blue. What seems to be missing is the Modifier
value. Now as to translating this into something you can use, I was
unable to find those settings (or any close) in the color master
charts from my old color grading class. My best translation based on
what you have described is a yO color, a 2 saturation, and maybe a 2
in tone. IE a yO22 or yO23 color. This would give you a color grade
for Citrine of a 2 1/4 to 3 on a scale of 1 to 10 with 10 being the
most desirable color for that species.

A though would be to contact the GIA and get a translation of the
colormaster notations into a more accurate description.

Hope this helps
Don