The Ultimate Expert-Approved Diamond Buying Guide

Let us help you strike the perfect balance between value and beauty.

Diamond buying guide

Read this comprehensive guide to discover how to choose the best diamond, what makes a diamond valuable, and the different considerations that go into purchasing the perfect diamond.


The word diamond comes from the ancient Greek αδάμας, meaning “unbreakable.” A diamond is perhaps one of the most storied gemstones in the world, and for good reason: it is the hardest naturally occurring substance, and its beauty is effortless to witness, even while arising from such complex formative processes.

Of course, it is completely understandable that choosing one of these special stones, especially when doing so for someone else, might create a pressure similar to that necessary for carbon to turn into diamonds (24-136 gigapascals of atmospheric pressure, incidentally).

Your Budget

At Steve Rosdal, we firmly believe there is no set rule for how much you should spend on a diamond. While these stones last a lifetime, it is important to feel comfortable with the amount you choose to spend. Your buying experience should be personalized to your needs and your loved one’s tastes (check out How to Choose the Most Beautiful Engagement Ring for more on this).

Your budget is a decision that can help narrow down your choices. While it may seem paradoxical at first, we can actually expand your possibilities and maximize the value of your diamond when we have a spectrum to focus on.


There are many diamond shapes, and you may not be familiar with all of them, but we can source any shape you’re looking for. Some popular shapes include round, princess, cushion, radiant, pear, oval, marquise, asscher, heart, and emerald.

round diamond 2Image

A round diamond is the most popular shape because diamond cutters have optimized its brilliance and fire over many years. Brilliance refers to the colorless light that emanates from the gem, and fire refers to the radiant, colored dispersion that occurs under light.


Princess diamonds are the second-most popular shape, often having the brilliance of a round diamond at a lesser cost.


Cushion and radiant diamonds are great choices for those who seek a softer rectangular shape.


Pear, oval, and marquise diamonds are uniquely shaped, often thinner with stunning edges.


Asscher and emerald diamonds have exquisite step facets for maximum brilliance.


Size refers to the actual dimensions of your stone, but often carat weight can be used to estimate the size, too. It is helpful to decide whether size, quality, or a balance between them is most important to you in your purchase.

The 4 C's

The key to a diamond’s value is rarity, and no two diamonds are alike. Rarity is determined by a diamond's unique characteristics as measured by the 4Cs: cut, color, clarity and carat weight. Using these criteria, a small diamond of exceptional quality will likely be more valuable than a larger diamond of lower quality.

The 4 C’s were developed by the Gemological Institute of America (GIA), an internationally respected research institute that certifies every one of our diamonds. Most of our stones come with a comprehensive GIA report that evaluates its attributes, including the 4 C’s.

Carat Weight

The metric carat is the standard unit of weight for diamonds and most other gems. A carat weighs about the same as a small paper clip.

It’s true that the larger a diamond is, the more valuable it tends to be. However, bigger is not necessarily better. Two diamonds that have the same carat weight can differ significantly in value and price. This is because the 3 other C’s are incredibly important to the quality of a diamond.


What makes a diamond sparkle? What many people don’t realize is that the most important key to a diamond’s radiance is its cut.

The craftsmanship of a diamond’s cut will deeply influence its fire, brilliance, and scintillation (the flash and reflection of light). A higher cut grade means a better-proportioned diamond, meaning that the stone will reflect maximum light, and different colors will glint magnificently.

Cut affects both the weight yield from rough and the optical efficiency of the polished stone; the more successful the cutter is in balancing these considerations, the more valuable the stone will be. The GIA Cut Scale ranges from Excellent to Poor.


A gem’s color actually refers to the absence of color— the less, the better. Most diamonds have at least a trace of yellow or brown in their body color. With the exception of some natural fancy colors, such as blue, pink, purple or red, the colorless grade is the most valuable.

The GIA Diamond Grading System uses letters to represent colors, beginning with D (colorless) and ending at Z (light yellow or brown). Many people prefer colorless or white diamonds, and the most popular grade is F-H, meaning it is near colorless or has faint color.


Clarity refers to the stone’s characteristics regarding blemishes and inclusions, meaning its visual imperfections. The GIA Clarity Scale includes 11 grades, from F (flawless) to I (imperfect). The size, number, position, nature, and color or relief of these imperfections determine the clarity grade.

Usually, clarity is a less significant grade, having the least visual impact on a diamond’s beauty. If other factors are equal, flawless stones are most valuable. Very few diamonds are flawless (showing no inclusions or blemishes under 10x magnification).

Inclusions and blemishes can look white or black. They can resemble crystals, cavities, clouds, or needles.

Check out GIA's interactive 4 C's charts on our Education page -->

Learn more from the diamond experts

Check out our related blog post, How to Choose the Most Beautiful Engagement Ring.


We hope this guide has been crystal-clear.

If you have any questions about choosing the best diamond for your needs, please feel free to contact us at (720) 379-6505.

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