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Because two diamonds of equal weight may differ in

value by thousands of dollars based on color, jewelers and

wholesalers of precious gems need to have confidence that

the products they carry have been graded accurately under

precise lighting by qualified people.

With the difference between “pricey” and “priceless”

hanging in the balance, they turn to GIA (Gemological

Institute of America) laboratories to provide accurate

identification and grading of diamonds, colored gemstones

and pearls.

And when it comes to color, GIA turns to X-Rite Inc. to

lend expertise on assessing the color vision of grading

technicians and providing the optimum lighting conditions

for accurate gemstone evaluation.

The color of gemstones can look vastly different depending

on how they are illuminated, says John King, GIA’s chief

quality officer, which has gem identification and grading

laboratories in New York City, Carlsbad, Calif., Bangkok,

Hong Kong, Mumbai, Johannesburg and Gaborone,

Botswana.

Colored gemstones will look different under natural

daylight depending on a number of factors such as the

time of day, the season, weather and city where they are

being viewed. For instance, blue sapphires may show a

beautifully saturated color under noon daylight, but appear

darker in the early morning or late evening hours.

Given the variable nature of daylight and fact that it is

not always available, GIA has adopted the calibrated

illumination of the Macbeth Judge II light booth

manufactured by X-Rite for use in its laboratories. The

Judge II is capable of accurately replicating noon daylight

and the horizon light at sunrise and sunset, as well as the

“average” fluorescent and incandescent light sources a

person may find in a retail store or at home. It also provides

an adjustable source of invisible ultraviolet light, which is

present in natural daylight and can cause certain gems to

shine brighter.

“In the early 1990s, when we were considering

refinements to our system for color-grading diamonds, we

looked at a number of viewing environments,” King says.“We wanted something readily available because we want

the tools we use in the lab to be accessible to the trade.

The Judge II is available worldwide, it provides a good

fluorescent light source, and it’s well-known within our

industry.”

A Cut Above The Rest: GIA Uses X-Rite Tools to Ensure the Color of Gemstones Are

Certified Accurately

GIA Case Study

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While the majority of GIA’s colored gem

evaluations take place in its laboratories

in Carlsbad, New York City and

Bangkok, King says the institute has

begun to look at its other lab locations

as well, which makes the Judge II’s

portability another plus. “We’ve taken

parts of the equipment on the road

with us to simulate the evaluations

done in our labs,” he says, “and the

Judge II has proven quite useful in

these demonstrations.”

Precisely controlled lighting is only one

variable in accurate gem grading, King

says. The technicians themselves need to have normal

or exceptional color vision if they are to grade precious

stones, and a surprising segment of the populace has someform of color vision deficiency. Studies indicate that about

one in 12 males and one in 255 females have some form

of color blindness.

“Some differences in gemstone color are extremely subtle,

but our work requires accuracy and consistency,” King

says. “Our graders go through rigorous testing to assure

they have the visual acuity necessary for the job.”

One of the key evaluations used by GIA for would-be gem

graders is the Farnsworth Munsell 100 Hue Test, a sort

of “color IQ test” made by X-Rite that helps companies

distinguish between employees with low, average or

exceptional color vision. Individuals being assessed for

color vision often can complete the FM 100 Hue test in less

than 20 minutes, and a person can be trained on how to

administer the test in about 5 to 10 minutes. Because the

test is quick and effective, companies will often test their

employees annually to assess whether their sense of color

discrimination has changed over time.

Simplicity is a hallmark of the FM 100 Hue test. The

person administering the test gives the participant

four trays holding a total of 85 color chips in randomorder. The chips have different hues, but identical value

(lightness) and chroma values. The object of the test is

for the participant to arrange the chips in proper order by

hue. The misplaced chips are counted, with lower scores

signifying better ability to discern color differences.

Each gem generally is evaluated by several GIA graders

working independently, with no knowledge of the stone’s

origin, ownership or ranking by others, until consensus on

its quality is achieved.

The actual process of evaluating a gemstone in the

laboratory may take only a few minutes, but a single

gemstone is evaluated several times by different

individuals. A bar-coded but otherwise anonymous gem is

placed in the light booth and compared with GIA’s existing

samples.

Considering the potential value of any given gemstone,

GIA’s multiple evaluations and anonymous labeling

for the laboratory help ensure each stone receives a

comprehensive review and a fair, objective assessment ofits worth.

“GIA is a standards organization, so the continuity of

what we do and how we do it is vitally important,” King

says. “The independence of our graders, the checking and

double-checking, are all designed to maintain the quality

and integrity of our work.

“X-Rite’s tools help us to maintain that integrity of accurate

color evaluation,” he adds.

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