DIAMONDS 101  - THE 4 C’s: Cut, Color, Clarity, Carat Weight


When a diamond is cut with the ideal proportions for its shape, it reflects more light out of the top, producing incredible fire and brilliance. A poorly cut diamond with incongruous proportions looks dull and dark because it allows light to escape out the bottom and sides. In short, a well cut diamond sparkles a lot because it reflects and refracts light better than one not cut as well. A good cut increases price.




In the world of white (technically, colorless diamonds) it is the absence of color which is prized. The GIA standard for color grading is a scale which extends from D (colorless) to Z (light color). Diamonds darker than Z are considered Fancy Color. Although the scale most typically refers to diamonds possessing some tint of yellow, the scale can also be applied to diamonds possessing a tint of grey or brown.

© American Gem Society 


The Gem Lab suggests that your search for a diamond begin in the color grade range of F to I color. In this range, the “face-up” appearance of the diamond will be white. If mounting the diamond in a yellow gold setting, a diamond in the J to L color range may be quite acceptable. 

Below is a group of round diamonds ranging in size from 1.02ct to 1.21ct. representing GIA color grades E through L, GIA clarity grades VVS-2 through SI-1 and AGS Cut Grades 0-3 (Ideal to Good).


© The Gem Lab


Please notice that there is much LESS difference in their actual appearance than the color grade would lead you to believe.

Any one of the six gemologists (GIA, Gem-A) on The Gem Lab staff can demonstrate the subtleties of color grading on your next visit.





The clarity grade of a diamond is a verbal representation of the ease with which a diamond’s internal characteristics are detectable and their effect on the visual appearance of the diamond. The clarity grade is a combination of five different elements….size, nature, number, location and relief. Size: Larger size equals lower grade. Nature: Internal versus external Number: Generally, a greater number of inclusions will lower the clarity grade. However, the size and position of those inclusions are taken into consideration. A single larger, darker crystal inclusion will lower the clarity grade more than a dozen white pinpoint inclusions. Location: Inclusions located closer to the center of the diamond are generally easier to see. Inclusions located near the pavilion can sometimes be reflected numerous times within the diamond. Relief: the distinctiveness of the inclusion relative to the diamond can affect the clarity grade.


© Gemological Institute of America (GIA)

Flawless/Internally Flawless (0 or 0*)
Flawless and Internally Flawless diamonds contain no internal inclusions when examined by a skilled grader under 10x magnification and in a proper gemological environment.  An Internally Flawless diamond may have minor blemishes (marks and features confined to the surface only).

Very Very Slightly Included (1 or 2)
A diamond with a clarity grade of 1 or 2 (VVS1 or VVS2) has minute inclusions that are difficult for a skilled grader to see under 10x magnification.

Very Slightly Included (3 or 4)
Very Slightly Included diamonds with a clarity grade of 3 or 4 (VS1 or VS2) have minor inclusions.

Slightly Included (5 or 6)
Slightly Included diamonds with a clarity grade of 5 or 6 (SI1 or SI2) have noticeable inclusions that are fairly easy to see under 10x magnification.  Sometimes, these inclusions can be visible to the unaided eye.

© American Gem Society (AGS)


Internally Flawless (tiny scratch adjacent to facet edge)


VVS-1 (tiny pinpoint)








SI-1 (Dark Crystal)

SI-2 (White feather at 9:00) 





Carat Weight refers to size and weight. Larger diamonds are scarce, and therefore more valuable. However, two diamonds with the same carat weight can vary greatly in value, depending on the color, clarity and most importantly, the cut. A half-carat diamond with high color and clarity ratings may cost more than a three-quarter carat diamond with lower color and clarity ratings, but identical cut. It’s simply a matter of deciding what matters most to you, size or quality, then finding the best combination of size, color and clarity to suit your budget.

Diamond weight is the one objective grading characteristic of diamonds. There are is no confusion based on estimates, comparisons or judgments. One carat is equal to 1/5 (0.200) gram. It is further divided into 100 “points”. 50 points = 1/2ct, 75 points = 3/4ct and so on. Diamonds are weighed on a precisely calibrated digital balance to the third decimal point. Unique to the diamond industry, “rounding up” is done when the third decimal is 9, not 5. Example: 1.227ct = 1.22ct 1.229ct = 1.23ct.

Because most of a diamond’s weight is actually below the girdle outline of the diamond, the increase in a diamond’s weight is not reflected as much in it’s diameter as one might expect. A 1/2ct diamond measures about 5.00mm in diameter. A 1.00ct round diamond measures about 6.40mm. in diameter. The 1.00ct diamond can cost as much as twice the amount of the same quality 0.50ct diamond, yet it is certainly not twice as large in appearance.

The “price per carat” of diamonds increases as the size of the crystal increases. We see increases in the “price per carat” at every size category, e.g. 0.50ct, 0.60ct, 0.70ct. etc. Savvy buyers will consider that a 0.95ct diamond is VERY similar in physical size to a 1.00ct diamond, but may cost thousands less for the same quality.


At The Gem Lab, our trained gemologists will happily demonstrate the similarity of diamond sizes while helping you find the most beautiful diamond in your budget range.