This page provided more detailed information than is required for students of Geology 306
COLOR:
(1) Place the UNMOUNTED stone table down on a white surface (or in a gem trough) - look through the pavillion to the table or through the pavillion.
Sometimes a color - measuring device (colorimeter) is used, more commonly, grading is done by comparison with standards.
GIA scale: D (colorless) - Z (yellowish):
Note: each grade is ~ 7 - 15 % more expensive!
Note: most engagement rings are G to H.
The AGS scale goes from 0 to 10:
Colorimeter scales go from 1 - 10!
example:
GIA = E, colorimeter = 1.0 but AGS scale = 0 and colorimeter reading is 0.75!
Color of a fancy color diamond composes 60 % of its value!
Color may be:
exotic prices for pink diamonds!:
1 purple-pink 3.14 ct, $1.15M Apr 89 (JCK Nov 89)
13 pinks, total $551K Apr 89 (JCK Nov 89)
67 pinks 0.4 - 2.7 ct, total 64.13 ct, $6.9M total, Nov 89 (JCK Jan 90)
36 pinks, total 40.93 cts, over $2M total, (about $80K/ct for diamonds < 1.5 cts and about $100K/ct for 1.5+ cts) (JCK Dec 90)
FL - IF - VVS1 - VVS2 - VS1 - VS2 - SI1 - SI2 - I1 - I2 - I3
I = inclusions can be seen by a naked eye (need to take a look at a few of them before you will start seeing them)
Rest of the grading is done under a 10x microscope.
SI Using a microscope, you should be able to see the inclusions within about 5 seconds
VS probably takes a long time to find any inclusion on your own, assuming you are used to using the microscope.
VVS2 An expert would find it difficult to find an inclusion from the top of the stone
VVS1 An expert would find it difficult to find an inclusion from the bottom of the stone
IF internally flawless diamonds have no observable internal inclusions, only some on the surface that could be gotten rid off by polishing the diamond some more at the expense of weight.
FL diamonds are again extremely rare, there are only about four hundred 1 ct. FL diamonds produced per year worldwide.
(Source: Extracted from http://kaos.deepcove.com/cig/mlynek.html)
