The Quality of a Diamond

A diamond's beauty and value are determined by its quality. The main factors that determine the quality of a diamond are:

Color

Color refers to the amount of body color a diamond has, most commonly yellow or brown, but also rarely in pink, green, blue, orange, and fancy yellow.

The color of a diamond is an important characteristic because it is noticeable to the untrained eye.

GIA

D

E-F

G

H

I

J

K-L

M-N

O-P-Q

R-S-T-U

V-W-X

AGS

0

1

2

3

4

5

6

7

8

9

10

 

colorless
(collection color)

near colorless
(white)

faint yellow
(top silver)

very light
or light yellow

fancy yellow

Clarity

Clarity, or purity, refers to the amount of inclusions or imperfections in a diamond. Inclusions can be white spots, black spots, feathers, cracks or included crystals.

Generally, diamonds with an accurately graded clarity of SI1 or SI2 and higher will have no eye visible inclusions. Diamonds with I1-3 will have inclusions visible to eye without magnification.

To the unaided eye, a diamond with a Flawless grade will look identical to a diamond with a SI1 or SI2 grade.

  • Flawless: No inclusions under 10 power magnification
  • VVS1-VVS2: Very very slightly included. Very minor pinpoints only visible under magnification, so minute that it will take upwards of 30-40 minutes for a trained professional to locate using a microscope.
  • VS1-2: Very slightly included. Easier to find under magnification, but completely eye clean. May consist of a minute feather, minute black or white marks, or very faint clusters of inclusions.
  • SI1-2: Slightly included. Easy to locate under magnification. May include feathers, black or white marks, clusters, fractures, etc. but still only visible under magnification (some larger SI2 graded stones may have a very slight inclusion visible to the unaided eye).
  • I1-I3: Imperfect. Inclusions visible to the unaided eye. May include feathers, black or white marks, clusters, fractures, etc. Diamonds in the I2-I3 range usually have inclusions that effect the structural durability of the diamond and effect the diamond's brilliance.

GIA

FL

VVS1

VVS2

VS1

VS2

SI1

SI2

I1

I2

I3

AGS

0

1

2

3

4

5

6

7-8

8-9

9-10

flawless no blemishes

very very slightly included

very slightly included

slightly included

imperfect eye visible

Cut

The way a diamond is proportioned, or cut, determines how light is reflected by the diamond and determining its overall brilliance.

Cut and Proportion

A diamond's cut is one of the most important factors to consider when buying a diamond. A properly cut diamond will be bright and lively to the unaided and untrained eye compared to an improperly cut one. Diamond proportions may account for as much as 25% of a diamonds price.

A diamond's cut also determines how a diamond is proportioned and how it faces up in a mounting. An improperly cut diamond will not face, or show, the same diameter as a properly cut diamond.

For Example:

Properly cut:

Improperly cut:

1ct - 6.5mm diameter

1ct - 5.8mm diameter

3/4ct - 6mm diameter

3/4ct - 5.2mm diameter


A poorly cut diamond can have the same diameter as a smaller, properly cut diameter. The weight can be distributed to the diamond's pavilion (or bottom), to the girdle (center) or to the crown (top). This extra weight, however, has no benefit as is not seen. The smaller, properly cut diamond will cost less and be more brilliant than a larger, poorly cut diamond.

 

Factors that determine a diamonds proportions:

  • Depth Percentage
  • Table Percentage
  • Girdle Thickness
  • Culet Size
  • Crown Angle
  • Pavilion Angle

A diamond cut to maximum brilliance will have the proper relationship between table size, girdle size, crown angle and pavilion angle. There is not one ideal way of cutting a diamond as these factors can be combined in many ways to yield equally bright diamonds.

Cut also refers to the shape of the diamond. They are:

Round
Princess
Oval
Pear
Radiant
Marquis
Trillion
Cushion
Heart
Emerald

Carat Weight

The most common cut is the round brilliant. The princess cut is currently the second most popular cut and is a relatively new cut. Diamond pricing is relatively the same for most of the fancy shaped cuts with the round cut costing the most.

The last "C" refers to how much a diamond weighs (in carats). The chart above shows approximate diameters for properly cut diamonds in different carat weights.

Because larger crystals are more rare than smaller crystals, diamond pricing increases exponentially with the increase in diamond weight. A 1ct diamond is more than twice the amount of two 1/2ct diamonds.

For more information, visit The Gemological Institute of America (GIA) web site.