Diamond Terms, Decoded: The Carat Commons Guide to Understanding What You’re Buying
At The Carat Commons, we believe knowledge is power—and in the diamond industry, power has been hoarded for too long. Technical jargon and confusing certifications have been used to justify bloated retail markups and keep customers in the dark. We're here to change that.
This guide breaks down the real meaning behind the most common (and most misleading) diamond terms—so you can buy better, smarter, and with full confidence. Whether you’re choosing a lab-grown diamond for a custom engagement ring or investing in a loose stone, this is the clarity you’ve been looking for.
Understanding the 4Cs of Diamonds
The 4Cs—Carat, Cut, Colour, and Clarity—are the global standard for diamond grading. But each has layers the average shopper is rarely told.
Carat
Carat refers to a diamond's weight—not its visible size. One carat equals 0.2 grams.
A higher carat weight doesn’t always mean a bigger-looking diamond.
Elongated shapes like emerald, radiant, and oval cuts can face up larger than rounds of the same weight.
Cut
Cut is arguably the most important factor in a diamond’s beauty. It determines how well the diamond reflects light, which affects brilliance, fire, and scintillation.
Cut is graded from Excellent to Poor.
A well-cut diamond can appear brighter and hide inclusions, even in lower clarity grades.
Colour
Diamond colour is graded on a scale from D (colourless) to Z (light yellow or brown).
D–F are considered colourless and command a premium.
G–J offer great value and still appear white to the naked eye, especially in yellow or rose gold settings.
Clarity
Clarity measures the presence of internal flaws (inclusions) and surface marks (blemishes).
Here’s the clarity scale, from highest to lowest:
IF (Internally Flawless): No inclusions visible under 10x magnification. Ultra-rare, ultra-expensive.
VVS1–VVS2 (Very Very Slightly Included): Tiny inclusions, difficult even for a gemologist to detect.
VS1–VS2 (Very Slightly Included): Minor inclusions, usually invisible without magnification. Excellent balance of beauty and price.
SI1–SI2 (Slightly Included): Inclusions may be visible under magnification or to the naked eye, but often not noticeable in wear.
At The Carat Commons, we focus on sourcing eye-clean diamonds—stones that look flawless without paying for perfection you can’t see.
Beyond the 4Cs: Key Technical Terms You Should Know
The industry often hides behind complex terminology. Here's what matters and what to watch for:
Table
The flat top of the diamond. A larger table can enhance brilliance but may reduce fire if proportions aren’t balanced.
Crown and Pavilion
The crown is the upper portion above the girdle.
The pavilion is the lower section below the girdle.
Their angles affect how light reflects and refracts through the diamond.
Girdle
The thin edge between crown and pavilion.
Very thin girdles can chip; very thick ones add weight without adding visual size.
Medium to slightly thick is ideal.
Culet
The tiny point at the base of a diamond.
A small or no culet is preferred.
A large culet may appear as a dark spot when viewed from above.
Depth % and Table %
These ratios determine how light travels through the stone. Ideal ranges depend on shape:
For round cuts: 59–63% depth and 54–58% table
Other shapes have different optimal proportions—feel free to ask us for a shape-specific cheat sheet.
Lab-Grown Diamond Terminology
At The Carat Commons, we exclusively sell high-quality lab-grown diamonds. Here's the lingo worth knowing:
CVD (Chemical Vapor Deposition)
A method of growing diamonds layer by layer in a plasma reactor. CVD diamonds often have fewer inclusions and more consistent quality.
HPHT (High Pressure High Temperature)
A process that mimics natural diamond formation. It’s also used to enhance colour or clarity in some stones.
IGI, GCAL, and GIA Certifications
Diamond grading labs provide official reports. We use only IGI and GCAL for lab-grown diamonds—known for precision, transparency, and consistency. GIA is often used for natural diamonds.
Always read the full report, not just the grade.
At The Carat Commons, every diamond comes with a digital certificate and clarity video—no surprises.
Fluorescence
Describes how a diamond reacts under UV light.
None to faint is ideal for D–F stones.
Medium to strong blue fluorescence can make lower-colour diamonds appear whiter—useful for value buys.
Sales Tactics to Be Aware Of
We’re not just here to educate—you should know where traditional jewellers cut corners or spin stories.
Deep-cut stones may have hidden carat weight that adds cost without visual size.
Over-graded clarity or colour can come from less reputable labs.
Fancy terms like “Hearts & Arrows” are only meaningful if backed by a reliable cut grade.
The Carat Commons was built to challenge all of this. We cut out the middlemen, overpriced certification upsells, and opaque pricing structures.
Key Diamond Terms at a Glance
Carat = weight of the stone
Cut = craftsmanship that impacts sparkle
Colour = whiteness or tint
Clarity = visibility of inclusions
CVD / HPHT = how lab diamonds are made
IGI / GCAL = trusted grading labs
Table %, Depth %, Girdle, Culet = proportions that affect brilliance
Fluorescence = UV light reaction that can help or hinder appearance
Why It Matters: Diamond Clarity for a Clearer Future
When you understand the language, you take back the power. At The Carat Commons, we translate every technical term into plain English, back every stone with certification and video inspection, and help you buy better—not just bigger.
We’re not here to sell you the most expensive diamond. We’re here to help you get the most brilliant one for your budget—without the nonsense.
Explore our current inventory or contact us for a consult. We're here to unrig the diamond game, one cut at a time.