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A guide to diamonds

Jessica McCormack

Each Jessica McCormack diamond is hand selected for its unique qualities and guaranteed to come from legitimate sources that are not involved in funding conflicts and in full compliance with UN resolutions.

One of Jessica McCormack’s business partners, Michael Rosenfeld, is a third generation diamantaire and art collector whose love for diamonds is backed up with extraordinary knowledge of the diamond industry. Michael’s expertise in sourcing stones of exceptional quality and beauty enable Jessica to offer a unique selection of diamonds.

The 5 C’s

Traditionally, diamonds are classified by the four C’s: Cut, Carat, Colour and Clarity. At Jessica McCormack, we go beyond the standard classification by including a fifth C: Character. Michael and Jessica both strongly believe in a diamond’s personality. Together, they make sure that each diamond has a strong character shining through along with the other four standards.


The shape and proportions of a diamond are determined by its cut. Of all existing diamond shapes, the most recognised are the brilliant, oval, marquise, pear-shaped, heart-shaped, emerald and princess cuts.

Diamonds cut graphic


A carat is a standard unit to measure the weight of a diamond. One carat equals 200 milligrams. This can be divided into points, where 0.75 carats = 75 points. A diamond’s value varies according to its number of carats and its rarity. Diamonds may equal in weight but vary in price due to the difference in quality. This means that a smaller diamond with a high carat weight may be more valuable than a large diamond with a lower clarity, colour or cut.

Diamonds carat


Diamonds are graded from D (colourless) to Z (light yellow). The closer a diamond is to colourless, the more extraordinary and rarer it is.

GiaDescriptionOld world terms
D Colourless Jager Diamond D
E River
G Near Colourless Top Wesselton Diamond H
H Wesselton
I Top Crystal
J Crystal
K Faint Yellow Top Cape
M Cape M
N Very light yellow Very light yellow Diamond N
S Light yellow
T Diamond Z
Z Dark cape


All diamonds have imperfections called inclusions. These are formed deep within the diamond and occur naturally.

Clarity refers to the presence, visibility, number and size of inclusions in a diamond and is graded from flawless to included.

A diamond will reach a higher level of clarity depending on the flaws seen under the loupe. A perfectly pure diamond is extremely rare, and priced accordingly.

Diamonds clarity