Diamond Education & Buying Guide

At Breslauer & Warren, we have been working with diamonds since 1919 and have the expertise to ensure that you get the best quality diamond in the perfect setting. But if you are not an expert in diamonds it can be very difficult to tell the difference between a high quality diamond and a lower quality diamond. This can make it very intimidating for the average diamond shopper to make their decision with confidence. To help make diamond purchasing easier, we have compiled a “Diamond Education” guide to help you get a better idea of what to look for when buying a diamond ring or other piece of diamond jewellery.

Diamond Colour

The colour of a diamond is a very important characteristic that affects both the look and value of a diamond. A diamond’s colour is graded on the GIA scale from D-Z, with D being absolutely colourless and Z being light yellow. It is often very difficult to detect the difference between a colourless diamond and a near colourless diamond. Diamonds below the near colourless range will have a slight yellow tint that can be detected by the naked eye. A light yellow diamond with proper proportions and minimal clarity characteristics will still generate a nice brilliance.

Diamond Colour Grading Chart

Diamond Clarity

Since diamonds are formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, inclusions or blemishes. Inclusions are internal characteristics within a diamond whereas blemishes are characteristics related to the diamond’s surface. These characteristics can detract from a diamond’s brilliance and overall beauty. When a light vector enters a diamond, it is reflected off the facets and is returned to the eye as pure light. If there is anything disrupting the flow of light in a diamond, such as an inclusion, a portion of light reflected may be lost.

Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond’s value. Every diamond is unique. None are absolutely perfect under 10× magnification. Those that come close are known as flawless diamonds and are exceptionally rare.

On the GIA scale, diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I3). In determining a clarity grade, the size, nature, position, color, and quantity of clarity characteristics visible under 10× magnification is taken into consideration.

Diamond Clarity Variation Chart

Diamond Cut

Cut is the factor that fuels a diamond’s beauty and is considered to be the most important of the four C’s. Though extremely difficult to analyze, it is important to understand how a diamond achieves its brilliance, fire, and scintillation. There is no single measurement of a diamond that defines its cut, but rather a collection of measurements and observations that determine the relationship between a diamond’s light performance, dimensions, and finish.

There are many laboratories that determine the cut of a diamond. The top two laboratories in the jewelry industry are GIA and EGL. Each laboratory has its own terminology that is used when describing the cut grade of a diamond. GIA describes the cut using a range from Excellent to Poor, while EGL uses terms such as Ideal Plus, and Hearts and Arrows. This grading parameter has only been extended to Round Brilliant cut diamonds at this time. There is no industry standard for ideal or excellent cut diamonds other than Round Brilliant.

Polish and Symmetry are two important factors in the cutting process. Polish refers to the quality of a diamond’s surface, which can include nicks, abrasions, and polish lines. The symmetry grade refers to the alignment of the facets. Examples of poor or fair symmetry characteristics can include an off centered table, misshapen facets, or off center culet. On the GIA scale, the polish and symmetry are graded as follows: Excellent, Very Good, Good, Fair, and Poor. Breslauer & Warren recommends choosing a diamond with a polish and symmetry grade of good, very good, or excellent.

Diamond Light Reflection Chart

Diamond Carat

The weight of a diamond is measured in carats, which is a small unit of measurement. Each carat is divided into 100 points. Therefore a 0.50 carat, or a half carat, may be referred to as a 50 point diamond. Carat weight is the easiest of the 4 C’s for gemologists to determine because of the use of sophisticated measuring equipment. The measurements of a diamond are in direct correlation with its carat weight, if a stone is properly cut. Shallow or deep cut diamonds will not reflect the correct surface area the stone should have. The carat weight of a diamond has a large impact on the cost. The price per carat increases exponentially with the increase in weight. For example, the value of a 1 carat diamond will be greater than 2 half carat diamonds of equal quality.

Diamond Measurement Size Chart

Diamond Certification

GIA (Gemological Institute of America)
Established in 1931, the Gemological Institute of America is the world’s foremost authority on diamonds, colored stones, and pearls. GIA exists to protect all purchasers of gemstones, by providing the education, laboratory services, research, and instruments needed to accurately and objectively determine gemstone quality.

GIA is the most respected gemological laboratory in the world, entrusted with grading and identifying more gems than any other lab including the Hope, the Taylor-Burton, the De Beers Millennium Star, and the Incomparable. Located in major gem and jewelry centers around the world, GIA laboratories are staffed by expert diamond graders and gemologists, whose work sets the standard for grading practices worldwide.

Below is an example of a GIA diamond grading certificate:

AGS Diamond Certificate Sample

EGL USA (European Gemological Laboratory United States of America)

EGL USA is one of the largest and oldest independent gemological institutions focusing on gemstone certification and research. Originally part of an international network founded in Europe in 1974, EGL USA opened its first U.S. lab in the heart of New York’s international diamond and jewelry district in 1977.
In 1986 EGL USA became independently owned. Today, the EGL USA Group has laboratories in New York City, Los Angeles, Vancouver, and Toronto.
EGL USA is not affiliated with any other EGL labs outside North America.

Every certificate issued by EGL USA states, “A member of the EGL USA Group.” Certificate numbers are preceded by either “US” or “CA,” to indicate country of origin and to provide consumers the assurance that their certificate has been issued by a member of the EGL USA Group.

Below is an example of an EGL USA diamond grading certificate:

GIA Diamond Certificate Sample

IGI (The International Gemological Institute)

IGI is the largest organization of its kind, with offices in Antwerp, New York, Hong Kong, Mumbai, Bangkok, Tokyo, Dubai, Tel Aviv, Cavalese, Toronto, Los Angeles, Kolkata, New Delhi, Thrissur, Surat, Chennai and Shanghai . The IGI School of Gemology operates from Antwerp, Mumbai, Dubai and Cavalese, offering a variety of courses designed for professionals and consumer enthusiasts alike. IGI is the world’s largest independent gem certification and appraisal institute for diamonds, colored gemstones and jewelry.
Below is an example of an IGI diamond grading certificate:

IGI Sample Diamond Certificate