How Are Diamonds Graded?

Key Takeaways

• Diamonds are graded according to the 4 C’s: Cut, Color, Clarity, and Carat weight.
• Cut refers to how the diamond’s facets interact with light (fire, scintillation, and brilliance).
• Color evaluates the absence of color.
• Clarity is based on the presence of inclusions (internal flaws) and blemishes (surface flaws).
• Carats are used to measure the weight (rather than the size) of the diamond. 
• Diamond graders from third-party organizations use specialized magnification equipment to analyze the diamond’s cut, color, clarity, and carat weight. 
• A final diamond certification/grading report is issued with individual grades for each category.

In this diamond grading guide, we’re going to help you understand the 4 C’s of diamonds and how they’re evaluated by third-party specialists to produce an unbiased grading report. 

Here’s everything you need to know about diamond grading, explained by industry experts.

What Are the 4 C’s of Diamonds?

The 4 C’s of diamonds refer to Cut, Color, Clarity, and Carat weight, which are the four primary factors that determine the beauty and value of a diamond. 

Each C is individually graded. The data is used to create a report that tells the potential buyer essential details about the diamond.

How are diamonds graded specifically? Here’s a closer look.

Cut

Cut refers to the diamond’s structure, shape, and overall craftsmanship. Key elements are: facet arrangement, precision of its angles, symmetry, and proportions. These factors determine how the diamond interacts with light:

• Fire: Similar to a prism, fire is based on how the diamond disperses light into colorful, spectral flashes of rainbows.

• Scintillation: When the diamond or observer moves, the diamond twinkles and sparkles due to the facets refracting and reflecting off each other. This effect is called scintillation. 

• Brilliance: The total amount of white light the diamond reflects to the viewer is referred to as brilliance. An exceptionally brilliant diamond will have an intense and lively white shimmer.

Diamond Cut Grades

How are diamonds graded based on their cut? 

• Poor: Dark and dull

• Fair: Noticeably dim

• Good: Sparkles, but loses light

• Very Good: Sparkles vividly

• Excellent: Intense and lively reflection

Color

For this next section of our diamond grading guide, it’s important to realize that diamonds are evaluated based on their lack of color. Colorless diamonds are most valuable; diamonds with lower color grades will typically have traces of yellow or brown tints.

Color grades are based on a scale that runs from D to Z, with D being the highest possible grade.

Diamond Color Scale

How are diamonds graded based on their absence of color? Here are the elements of diamond color grading explained:

• Colorless: D, E, and F diamonds are considered to be colorless, meaning the naked eye struggles to detect even the faintest hint of color.

• Near Colorless: G, H, I, and J diamonds are considered to be near colorless, meaning they may appear colorless under certain circumstances, but show color when compared with true colorless diamonds.

• Faint: K, L, and M diamonds show visible warmth.

• Very Light: N, O, P, Q, and R diamonds have noticeable color.

• Light: S-Z diamonds have color tints that are even more noticeable than very light diamonds.

Clarity

How are diamonds graded based on clarity? For this section of our diamond grading guide, we’re going to look at the presence of internal flaws called inclusions and surface flaws called blemishes. These irregularities develop when the diamond is formed or grown.

Gemologists grade diamonds based on their purity. Here are the five factors of diamond clarity grading explained:

• Size: How small or large the flaw is

• Number: The number of flaws

• Position: The location of the flaw

• Nature: The type of flaw and whether it affects structural integrity

• Color: Whether the flaw is dark, white, or clear

The Diamond Clarity Scale

How are diamonds graded for clarity? They receive one of the following diamond certification grades:

• FL (Flawless): No visible flaws, even under 10x magnification.

• IF (Internally Flawless): Only shows surface blemishes under 10x magnification.

• VVS1/VVS2 (Very, Very Slightly Included): Flaws are extremely difficult to detect under 10x magnification.

• VS1/VS2 (Very Slightly Included): Flaws can be detected under 10x magnification with considerable effort.

• SI1/SI2 (Slightly Included): Flaws can be detected under 10x magnification.

• I1/I2/I3 (Included): Flaws are blatant under 10x magnification and may be visible to the naked eye.

Carat Weight

Finally, we have the most straightforward section of our diamond grading guide. How are diamonds graded according to carats? A carat is simply a unit of measurement that represents 200 milligrams. Carats specify the diamond’s weight, not its dimensions. Different cuts and shapes of the same carat weight may appear bigger or smaller depending on their depth. Carat is still often referred to as a proxy for size, but these nuances can help you better understand its use and its limitations. 

Reach out for Expert Guidance

If you still need diamond grading explained, get in touch for one-on-one assistance. We’re always happy to help. Explore engagement rings, wedding bands, and other fine jewelry made with the highest quality lab-grown diamonds and created gemstones.