How to Buy a Diamond


Carat is the measure of a diamond’s weight. The term is derived from the carob seeds that were used to balance scales in ancient times, since they were of similar weight. The loose diamond is weighed on a calibrated scale. (A carat equals 1/5 of a gram) 100 points equal 1.00 carat and thus 50 points equal ½ carat.

As a diamond increases in size, it becomes rarer and its cost increases exponentially: Therefore a 1.00 carat diamond will cost considerably more than twice as much as a .50 carat stone of equal quality. But carat weight can be very misleading for diamonds of equal carat weights can have huge disparities in price based on Cut, Color & Clarity.


The attribute, “Cut”, has two distinct meanings: the shape of the diamond and the quality of the cutting. The Round Brilliant cut is by far the most popular and has been the top-selling diamond shape for more than one hundred years. When cutting Round Brilliant diamonds, the cutter must adhere to a set of strict guidelines. The Round Brilliant optimizes a diamond’s unique ability to reflect light and to sparkle. Three components comprise “Cut”. They are: proportions, symmetry and polish. Recently the GIA introduced a Cut Grade that evaluates and weighs all of these components in determining the quality of the “Cut” of a Round Brilliant (Excellent, Very Good, Good, Fair and Poor).

Well Cut Stone

All light reflects back through its top. This stone will be the most brilliant.



Poorly Cut Stone – Too Flat

The stone appears larger ​than a well cut stone of the same carat weight but is ​less brilliant.

Poorly Cut Stone – Too Deep

The more deeply cut diamond that is of the same weight as a properly cut diamond will appear smaller and be less brilliant.

All the other diamond shapes are referred to as “fancy” cuts. Among fancy cut stones, the brilliance of the round standard is rivaled only by the square princess cut and its cropped-corner cousin, the radiant cut. The emerald cut is elegant and always popular and is an example of a “step-cut” diamond. The antique cushion cut has been updated to a new more brilliant fancy cut diamond.


 Clarity is the evaluation of a diamond’s internal and external characteristics. The fewer inclusions or blemishes, the more valuable the diamond becomes. To locate most of these tiny characteristics, a jeweler will use a ten-power diamond loupe, then, evaluating the size, location, nature, number, and color of all the inclusions and blemishes, a clarity grade is assigned.

There are six main categories:

– Flawless (FL): Extremely rare with no inclusions or blemishes.

– Internally Flawless (IF): No inclusions and only minor blemishes.

– Very Very Slightly Included (VVS1-VVS2): Very minute inclusions seen with a 10 power loupe.

– Very Slightly Included (VS1-VS2): Minor inclusions seen with a 10 power loupe.

– Slightly Included (SI1-SI2): Noticeable inclusions seen under a 10 power loupe and a small percentage may be visible to the naked eye.

– Included (I1, I2 & I3): Obvious inclusions seen by the naked eye.

Please note that inclusions are visible to the naked eye only in the I grade. In most cases, there’s no link between clarity and beauty.


Diamonds come in every color of the spectrum, but the most popular are the colorless and near colorless (D-J). Truly colorless, pure white diamonds are extremely rare and, therefore, the most costly. Laboratories, like GIA, grade stones according to how far they deviate from colorless. Colorless stones are graded D,E, or F (see chart below). All three grades are considered colorless but with slightly more color. Color grading continues down through the alphabet, with each letter designating a slightly darker or warmer tint. The best way to see the true color of a diamond is by looking at it upside down against a white surface.

Color Scale: D – F

Color Scale: G – J

Color Scale: K – M

Color Scale: N – P

Colored diamonds, known as Fancies, are valued for their depth of color, just as white diamonds are valued for their lack of color. Fancy color diamonds are graded in order of increasing intensity from Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Dark and Fancy Deep.



Decide when you would like to propose and allow enough time to do both your research and have the ring completed. Often you will find the ultimate ring ready to go. Are you able to determine her size in case we have to custom make the engagement ring? Custom work can take from one day to four weeks depending on the designer and other factors.



The recommended guideline is two months salary; however, you should establish a budget that is realistic for you. It is best to take into account the size and quality of the diamond combined with the design of the mounting. The metal you choose: yellow gold, white gold, or platinum will affect your cost.

Whether you decide to surprise her or include her in the selection process, style is one of the most important factors in choosing a ring. What best reflects her taste in jewelry? Is she more classically traditional or does she prefer a contemporary design? Should it be simple or have more diamonds in the ring? Many couples pre-shop together to narrow the choices. Perhaps she has dropped subtle hints or been more direct and sent images of her ideal ring?



These factors will affect the price and impact of the ring. For the same money you may choose a smaller or larger diamond with varying grades of the Four Cs: carat weight, color, clarity, and cut. Most people feel the clarity does not affect beauty as long as the inclusions are not visible to the naked eye, while good color and cut make your diamond look brighter and sparkle more. We can show you options side by side to demonstrate such factors.



Buying a diamond engagement ring is one of the most important purchases you will make. When you are buying an engagement ring, it’s important to know and trust the company you’re buying from. E.B. Horn has a history and reputation for providing service, quality, and value in a family environment. You can take great comfort in the fact that we will be here for all your future needs and to service past purchases for years to come.

New Englanders have trusted family owned and operated E.B. Horn Co since 1839.


429 Washington Street
Boston, Massachusetts 02108

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