Tobin understands that purchasing a diamond can be intimidating to most. Our goal is to eliminate the intimidation in order to make your jewelry buying experience a positive one. We hope you find the following tips helpful. If you should have additional questions we encourage you to email or stop by our location to speak with our certified gemologists.
Conditions for evaluating a diamond
The number one key to buying a diamond is to select what fits your personal taste. The best condition for evaluating a diamond is face up at varying amounts of light. More light will show the sparkle, while low, indirect light will demonstrate how well the diamond transforms even the tiniest amount of light.

The allure of a diamond is affected more by cut than any other attribute. This is because the cut of a diamond affects the fire, sparkle and brilliance—in essence, it provides the ‘wow factor’ of a diamond! The standard diamond shape is round brilliant, but other shapes, such as heart and oval, are included in the category “fancy shapes.”

Cut is graded in terms of proportion, symmetry, and finish. When a diamond is skillfully cut, light will reflect and move through it efficiently—thereby creating the breathtaking sparkle that diamonds are famous for. The Gemological Institute of America has set a standard grading system by which diamonds are rated. The highest rating is Excellent, followed by Very Good, Good, Fair, and Poor. Because cut has such a great impact on the stone’s appearance, it should be a heavily considered factor when diamond shopping.


Most diamonds aren’t truly colorless—in fact, nearly all diamonds have varying amounts of yellows and browns. Since even tiny variations in color can substantially impact value and price, it is important to know how color is rated. The industry standard color rating scale, set by the Gemological Institute of America, rates color from D (perfect colorlessness) to Z (light color).

Professionals rate diamonds by closely analyzing them under controlled lighting. Each diamond is consistently measured against a scale that clearly defines each letter. Slight differences invisible to the untrained eye can make a substantial impact on diamond quality and, ultimately, price.

See the image below for examples of color variation in diamonds:


The old adage is true—no two diamonds are the same. That is because they form deep within the Earth under extreme heat and pressure, resulting in unique birthmarks. These birthmarks are identified under 10X magnification by a skilled grader. Marks on the inside of the diamond are called inclusions, while marks on the outside are called blemishes. The presence and severity of these marks determine the diamond’s clarity rating.

The Gemological Institute of America rates clarity on a scale of 11 grades ranging from flawless (FL) to diamonds with obvious inclusions (I3). While no diamond is perfect, a diamond labeled flawless contains no obvious marks under 10X magnification. Flawless diamonds are so rare that few jewelers have even seen one! Fortunately, many diamonds available have only slight imperfections that will have little effect on transparency and brilliance.

The image below demonstrates examples of clarity:

Carat Weight

The first thing many people notice about a diamond is carat weight. The reason is simple—more carats mean more diamond! The carat is a metric unit equal to .02 grams, about the weight of a standard paperclip. Each carat is divided into 100 points, so a half-carat diamond may be considered a 50-point diamond.

When it comes to value, bear in mind that larger diamonds have a greater value per carat because they are more rare. For instance, a 1.5 carat diamond will be several times more expensive than 3 half-carat diamonds of equal quality. It is also important to remember that two diamonds of equal carat weight could have great differences in value. This is because cut, color, and clarity also have great influence on the appearance and value of a diamond.

To compare the various sizes of diamonds, see the illustration below:

Shape of Diamond

Shape refers to the diamond’s form as viewed from above. The beauty of the shape is a matter of personal preference. The classic round cut has long been the most popular shape, but there are a variety of shapes available to suit personal taste:

Fluorescence refers to the effect of a diamond producing light when exposed to ultraviolet radiation. Under normal conditions, this effect is not detectable by the human eye. Diamonds with a strong fluorescence are generally priced lower than those with low fluorescence. Controversy does exist over whether fluorescence is beneficial or harmful to the value of a diamond. Therefore, the 4c’s (color, cut, clarity, carat) are generally considered more important than fluorescence.
Diamond Quality Certificate
Tobin Jewelers is proud to provide a Diamond Quality Certificate for every Hearts on Fire Diamond and most of our other quality diamonds. A diamond certificate provides information pertaining to the quality and grading of any diamond .75 carats or larger. This certificate is provided by the American Gem Society and is universally accepted by the jewelry industry as a document of authenticated quality. This certificate provides the rank for the diamond, which incorporates the grading of the cut, color, and clarity. A scale of zero to ten is used with zero indicating the rarest and most valuable and ten indicating the least desirable. This certificate ensures that you have an accurate assessment of your diamond. As a consumer you have the right to view this document prior to your purchase.
Choosing a Jeweler

Perhaps one of the most important things to consider when making a diamond purchase is the quality of the jeweler. It’s important to choose a jeweler with a positive reputation, strong credentials, and a customer satisfaction guarantee.

  •  Will the jeweler stand behind the quality?
  •  Do they have the expertise to provide you with a quality piece of jewelry that fits your needs?
  •  Do they offer repair services?
  •  Do they offer cleaning services?
  •  Do they offer financing options?
  •  Do they care about you as a customer?
  •  Do they have a positive reputation in the community?
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