At Denver Diamond Source, your local diamond store, we believe in transparency, honesty, and informing our clients.

While there is no match to viewing jewelry and gemstones in person, there are certainly some basics you can learn about online that will make you feel more confident when it comes to jewelry.

Dia Appraisal Equip

Diamonds: the 4Cs

In order to codify aspects of diamonds that influence value, the Gemological Institute of America came up with “the Four C’s”:

Cut, Color, Clarity, and Carat

Knowing about the 4Cs is a great first step to learning about diamonds.

An Assortment of Diamond Cuts
An Assortment of Diamond Cuts


Cut refers to:

  1. overall shape of the diamond
  2. the proportions of the diamond


The most common and classic diamond cut is the Round Brilliant Cut, also known as a “round” or a “brilliant cut.”  This cut utilizes the proportions of its 58 facets to maximize both brilliance (bright white light) and scintillation (spectral or rainbow light) in order to show the best sparkle. 

Other common center diamond cuts include: oval brilliant cut (aka oval), cushion brilliant cut (aka cushion), marquise brilliant cut (aka marquise), square brilliant cut (aka princess cut), and a cut-corner rectangular brilliant cut (aka radiant cut). 

There are other popular diamond cuts as well called step cuts.  The two most popular step cut center stones are emerald cuts and square emerald cuts (the former of which is known popularly, though not in accordance with copyright law, as Asscher cuts after the man who invented the cut.  There is still an Asscher company today.)

The magic of a diamond is unlocked in its ability to reflect and refract light (or sparkle).  It is the other elements of cut that make this possible: proportion, symmetry, and polish. Proportion: makes sure that the stone isn’t too deep or too shallow. If it’s too deep or shallow, a diamond has dark, grey or blackish areas.  These areas are “dead” areas that loose the light instead Symmetry: the stone is symmetrically cut. Polish: the actual cutting is done well; for instance, a cutter didn’t leave too many cutting marks on the stone that are etched into it. Diagram to right and photo of three diamonds below, courtesy of GIA
Three Diamond Cuts
Gia Cut Scale

The three round brilliant cut diamonds at left range in cut grade from “Excellent” at left, “Good” in center, and “Poor” at right.


For a normal diamond – the white, clean, clear diamond we know and love – the GIA assigns a color spectrum starting at D and ending at Z with D being the most colorless and Z having the most color. 

This does not include Fancy Color Diamonds, which are graded on a separate scale.

The color categories are Colorless, Near Colorless, Faint, Very Light, and Light.

Diamond Color
GIA Color Scale


Because diamonds form deep in the earth when carbon is under intense heat and pressure, certain natural characteristics can form, which is how clarity is graded. 

Clarity refers to the number, size, scale, color, and placement of natural characteristics (inclusions for interior characteristics or blemishes for exterior characteristics) in a diamond. 

A diamond’s clarity is graded by GIA gemologists with at least 10x magnification. 

On a GIA certificate, a diamond isn’t just graded; its inclusions and blemishes are plotted (which is like mapping) as well.


Flawless (FL): No inclusions or blemishes seen by a trained grader under magnification

Internally Flawless (IF): No inclusions are visible under magnification.  Minor blemishes (imperfections or characteristics limited to the outside of the stone) are.

VVS1 – VVS2: Inclusions or blemishes are very difficult for a trained grader to see under magnification.

VS1-VS2: Inclusions or blemishes are difficult for a trained grader to see under magnification.

SI1-SI2: Inclusions or blemishes are slightly noticeable to noticeable for a trained grader to see under magnification.  In certain instances, an SI2 has an imperfection visible to the naked eye.   

I1, I2, I3: Inclusions or blemishes are extremely visible under magnification and are most likely visible to the naked eye.  These imperfections may effect transparency and brilliance.

Gia Clarity Scale



The term “carat” refers to the weight of a stone.  A “carat” is a metric measurement of weight equal to 200 milligrams. 

One carat is divided into 100 points; for example, a diamond that is a tenth of a carat (0.10 ct) can be refered to as a “ten point diamond.”

If a stone is over one carat, then it’s still weighed to the hundredths place, but we would say a stone is “one-point-fifty-eight carats” rather than “one carat and fifty-eight points”.

Of course, a larger stone has a larger weight, but cut and proportions also help determine how large a stone looks.

Individual diamond proportions vary, but this chart to the left gives an approximate idea of how big different round brilliant cut diamonds are in millimeters.

Coming soon:

Fancy Color Diamonds

Fancy Color Diamonds