Several loose round cut diamonds on a gray table with one held in tweezers.

The 4C's of Assessing Diamond Quality

In the late 19th century when diamond mining really began in South Africa, diamonds were referred to as river or water diamonds if they were colorless, and Cape diamonds if they were pale yellow. Diamonds were either made well or made poorly. Almost 100 years later, in the 1940’s, Robert M. Shipley, the founder of the Gemological Institute of America (GIA), coined the term “4Cs” to help teach his students the four characteristics of a faceted diamond. These are color, clarity, cut, and carat weight. These four factors, along with the GIA International Diamond Grading System™, meant that diamond quality could now be assessed with a universal language, and purchasers knew exactly what they were getting.

Diamond Cut

The cut of a diamond is the arrangement of the facets in the stone, which affects the price and beauty of the diamond. How much a diamond will reflect light varies on the skill and craft of the diamond cutter. When precisely cut, the diamond’s light gets reflected from one facet to another resulting in a burst of brilliance.

Various images of diamond cuts

10 different cuts of diamonds labeled with text, "Round Brilliant, Emerald, Cushion, Oval, Heart, Radiant, Marquise, Princess, Pear, Asscher

Brilliant Cut

These diamonds have 58 facets, and they appear to radiate from the center through the top of the diamond. This cut of diamond is popular because it maximizes sparkle and shine. Brilliant cut diamonds include the round brilliant, pear, marquise, heart, and oval cut diamond.

Step Cut

This cut resembles stairs or steps and has three concentric rows of facets. Examples of step cut diamonds are emerald, asscher, baguette, and carré.

Mixed Cut

Mixed cut is a combination of step cut and brilliant cut, as exemplified in the princess, cushion, and radiant cut diamond.

Older Cuts

Cuts of diamonds that existed before the modern round brilliant was created include old European, rose, old mine, and single cut (still used today in modern jewelry).

Diamond Clarity

The grading system for measuring the type and size of impurities in diamonds was established by the GIA. Diamonds receive the FL (flawless) grade when there is no inclusion or blemish that interferes with the passage of light going through the stone.

Diamond clarity chart for grading

Diamond clarity chart visualizing 6 types of clarity and inclusions with text, " Diamond Clarity Chart: Diamond clarity refers to the absence of naturally occuring inclusions within the stone or blemishes on the surface. The grading of a diamond's clarity depends on the size, colour and location of any inclusion or blemish, and is assessed by 10x magnification. FL - FL diamonds are Flawless. IF - IF diamonds are Internally Flawless. VVS1/VVS2 - VVS diamond (1 and 2) are Very Very Slightly Included. VS1/VS2 - VS diamond (1 and 2) are Very Slightly Included. SI1/SI2 - SI diamonds (1 and 2) are Slightly Included. I1/I2/I3 - I diamonds (1, 2, and 3) are Imperfect.

FL & IF – Flawless & Internally Flawless – no inclusions visible under 10x magnification

VVS1 & VVS2 – Very, Very Slightly Included – minute inclusions, hard to view under 10x magnification

VS1 & VS2 – Very Slightly Included – slight inclusions, visible under 10x magnification but not always visible to naked eye

SI1 & SI2 – Slightly Included – slightly more prominent inclusion, visible under 10x magnification but may not be visible to naked eye

I1 & I2 & I3 – Included – inclusions are obvious under 10x magnification and may be visible to the naked eye


The diamond color scale actually measures relative lack of color. The GIA has created a grading scale where a letter is assigned to the degree of colorlessness found in the diamond. Starting with D and going to Z, each letter denotes an increasing amount of light in the diamond.

Color chart for diamonds

Diamond color chart visualizing the 5 groups of diamond colors with text, "Colorless - D/E/F, Near Colorless - G/H/I/J, Faint Yellow - K/L/M, Very Light Yellow - N/O/P/Q/R, Light Yellow - S/T/U/V/W/X/Y/Z.

D – Highest color grade, completely colorless

E & F – Gemologists can identify traces of colors, even though stone appears colorless

G, H & I – Appear almost colorless because the untrained eye doesn’t see the hint of color

J, K & L – Faint traces of color, visible to untrained eye

M to Z – Body color becomes increasingly more visible to the naked eye

Beyond Z – called “fancy color” diamonds, body color is saturated, typically yellow or brown but can be other colors

Carat Weight

Although the carat of a diamond is often thought as synonymous with the size of the diamond, it is actually the weight of the diamond. One carat is equivalent to 200 milligrams or 0.2 grams, and is also divided into 100 points. Points are used for describing precise increments of weight within a carat. A diamond’s price per carat increases in proportion to the size of the gemstone. Two diamonds of the same weight can have also different values based on their color, cut, and clarity.

Diamond carat weight chart

Diamond size chart visualizing the size of various diamonds ranging from 0.25 CTW to 3.00 CTW with text, "Diamond Size Chart: How do diamond sizes compare? This image shows the carat (ct) weight and average diameter for various round brilliant cut diamonds. 0.25CT/4.1MM, 0.50CT/5.2MM, 0.75CT/5.9MM, 1.00CT/6.5MM, 1.50CT/7.4MM, 2.00CT/8.2MM, 2.50CT/9.0MM, 3.00CT/9.3MM.

Diamond Appraisal in San Diego

If you’re looking to get your diamond(s) appraised in the San Diego Area, Elliot Grunwald is the independent appraiser at the San Diego Gemological Laboratory. Contact us today to set up an appraisal appointment and to get more information on appraisal costs.