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Diamond Know-How
Every Diamond Tells a Story. Learn to Read It.
The 4Cs, the shapes, the certifications — demystified. A complete guide to understanding diamond quality before you buy, written for first-time buyers and seasoned jewellers alike.
4 Cs The universal grading system
D – Z Colour scale
FL – I3 Clarity grades
IGI · GIA Certified by world leaders
The Language of Diamonds
A Shared Standard, Since 1953.
The 4Cs — Cut, Colour, Clarity, Carat — were developed by the Gemological Institute of America in the mid-twentieth century as a universal grading framework. They've shaped every diamond transaction since, and they're still how the world talks about quality today.
"The goal isn't the highest grade in every column. It's the right balance for your purpose, your setting, and your budget."
Two diamonds of identical carat weight can differ dramatically in price and appearance — depending on how their other specifications balance out. A well-cut 1.00 ct with G colour and VS2 clarity will often look more striking, and cost considerably less, than a poorly cut 1.00 ct with D colour and IF clarity. Understanding the 4Cs means understanding where to invest and where to save.
Every AZENA stone is independently certified by IGI, GIA, or GCAL — the same laboratories that grade the world's finest mined diamonds. Every specification in every product listing has been verified by a third party. You know exactly what you're buying.
The Four Cs
Cut. Colour. Clarity. Carat.
Four measurements that define every diamond. Below, the essentials of each — what they measure, what to look for, and where the sweet spots live between quality and value.
The First C
Cut — The Most Important C
Cut is the only C shaped entirely by human skill. It measures how precisely a diamond's facets are proportioned, aligned, and polished to return light. A well-cut stone delivers brilliance (white light), fire (spectral colour), and scintillation (sparkle in motion).
Even a flawless, colourless diamond will look lifeless if its cut is poor. Always prioritise cut grade — it's the difference between a diamond that glows and one that hides.
Grades: Ideal · Excellent · Very Good · Good · Fair
The Second C
Colour — From D to Z
Colour grading measures the absence of colour in white diamonds, from D (completely colourless) to Z (noticeable yellow or brown). The closer to D, the rarer and more valuable the stone.
Most buyers find their sweet spot between G and H — all near-colourless grades that look identical to D in typical lighting. Beyond the D–Z scale, fancy colours — vivid pinks, blues, yellows — have their own dedicated grading system.
Best value range: G – H
The Third C
Clarity — Purity Under Magnification
Clarity evaluates internal inclusions and surface blemishes under 10× magnification. Every diamond carries a unique clarity fingerprint, formed during its growth.
VS1–VS2 is the practical optimum for most buyers: inclusions exist, but they're invisible to the naked eye — and the price gap versus IF or VVS is meaningful. Lab-grown diamonds routinely achieve top clarity grades thanks to their controlled growth conditions.
Best value range: VS1 – VS2
The Fourth C
Carat — Weight, Not Just Size
Carat measures weight, not dimension. One carat equals 0.2 grams, divided into 100 points. A 0.75 ct diamond is 75 points.
Prices jump at key thresholds — 0.50, 1.00, 1.50, and 2.00 ct. A 0.90 ct stone can cost 15–20% less than a 1.00 ct of identical quality, with barely any visible size difference. Shape matters too: an oval or pear looks larger than a round of the same weight.
Strategic tip: shop just below major thresholds
Colour at a Glance
From Colourless to Fancy.
The D–Z scale grades the absence of colour in white diamonds. Beyond Z lies the separate world of fancy colour stones — graded for hue, tone, and saturation.
D
E
F
G
H
I
J
K–M
N–R
S–Z
Fancy
COLOURLESSThe rarest grades
NEAR COLOURLESSBest value
SLIGHTLY TINTEDSubtle warmth
FAINT YELLOW
VERY LIGHT
LIGHT YELLOW
FANCY YELLOW
Ready to find your stone?
Filter by every C — cut, colour, clarity, carat — across 12,000+ certified diamonds.
At a Glance
The Clarity Scale, Explained.
Eleven grades from Flawless to Included. Most fine jewellery lives between IF and SI1 — but the best value typically sits in VS territory, where inclusions exist but aren't visible to the naked eye.
| Grade | Under 10× magnification | To the naked eye |
|---|---|---|
| FL — Flawless | No inclusions or blemishes | Invisible |
| IF — Internally Flawless | Only faint surface marks | Invisible |
| VVS1 – VVS2 | Minute — extremely hard to detect | Invisible |
| VS1 – VS2 | Minor — hard to detect | Invisible |
| SI1 – SI2 | Noticeable inclusions | Sometimes visible |
| I1 – I3 | Obvious inclusions | Visible |
Shape & Silhouette
Every Outline Carries a Character.
Shape is the first thing a buyer notices. Each silhouette has its own optical signature, its own design history, and its own balance of elegance and brilliance.
Round brilliants remain the bestseller for a reason — their 57-facet geometry is mathematically optimised for maximum light return. But fancy shapes — ovals, pears, emeralds — often deliver larger face-up size per carat, distinctive character, and better value per visible millimetre.
The right shape isn't the most expensive one. It's the one that speaks for the wearer.
- ◆Round Brilliant57 or 58 facets — the brilliance benchmark. Versatile in every setting, timeless in every decade.
- ◆Oval · Pear · MarquiseElongated shapes that maximise face-up size and elongate the finger. Excellent value per visible millimetre.
- ◆Emerald · AsscherStep-cut shapes with architectural lines. Emphasise clarity over sparkle — ideal for high-clarity stones.
- ◆Princess · Cushion · RadiantFancy brilliants combining geometric outlines with the sparkle of a round. Popular for modern engagement rings.
- ◆Heart & Custom CutsShapes with personality. Lab-grown technology unlocks bespoke silhouettes — kite, shield, signature fancy cuts, and more.
Designing a signature piece?
Commission custom shapes, calibrated sets, or bespoke specifications for your next collection.
The Finishing Details
Beyond the 4Cs.
Three more factors appear on every grading report — and decide how a diamond performs in the real world.
Polish
Surface Finish
The smoothness of each facet after cutting. Microscopic polish lines reduce light transmission and surface sparkle. Top-tier polish produces clean, mirror-like facets.
Look for: Excellent or Very Good
Symmetry
Facet Alignment
How precisely facets align and mirror each other. Poor symmetry misdirects light, creating visual noise. Especially critical in round brilliants and solitaires.
Look for: Excellent or Very Good
Fluorescence
UV Response
How a diamond reacts to UV light. Usually cosmetic — in lower colour grades, blue fluorescence can mask yellow tints. Very strong fluorescence in high-colour stones can cause slight haze.
Look for: None, Faint, or Medium
Diamond Anatomy
Physics in Every Facet.
A diamond's architecture isn't decorative — it's an engineered system for capturing and returning light. Five regions shape every brilliant-cut stone.
TABLE
- The largest facet of the diamond
- Flat surface on top
- Similar to a table-top
CROWN
- Extension above the girdle
- Ends at the girdle's top edge
- Step or brilliant-cut facets
GIRDLE
- The diamond's outer edge
- Widest point of the stone
- Meeting place of crown and pavilion
- Can be rough, faceted, or polished
PAVILION
- The bottom section of the diamond
- Bridge between girdle and culet
- Determines light reflection
- Cut quality shapes maximum light return
CULET
- The smallest facet
- Located at the bottom-most tip
- Protects the pavilion from chipping
- Often rendered as a single point in modern cuts
Independent Proof
Certifications You Can Trust.
A diamond without a grading report is a diamond without proof. Every AZENA stone is independently certified by one of three internationally recognised laboratories — the same labs that grade the world's finest mined stones.
Lab 01
IGI
International Gemological Institute. The world's largest independent gem lab, with broad adoption across the lab-grown diamond trade. IGI reports are trusted globally in retail and wholesale markets.
Lab 02
GIA
Gemological Institute of America. The institution that created the 4Cs grading system in 1953. GIA reports are considered the industry gold standard and carry maximum weight in high-end retail.
Lab 03
GCAL
Gem Certification & Assurance Lab. Known for rigorous light-performance grading and guaranteed certification accuracy. GCAL reports include optical brilliance analysis beyond the standard 4Cs.
How to Choose
Five Rules for Choosing the Right Diamond.
Not every buyer needs the highest grade in every category. What matters is the right balance for your setting, your design, and the wearer.
01
Prioritise cut above everything else.
A well-cut diamond in a lower colour or clarity grade will outshine a poorly cut stone with higher paper specs. If you must compromise, compromise on colour or clarity — never on cut.
02
Know the sweet spots.
VS1–VS2 clarity with G–H colour delivers the best visible beauty per euro. Inclusions are invisible, colour tints undetectable, and the price saving over IF/D is meaningful.
03
Shop just below weight thresholds.
Prices jump at 0.50, 1.00, 1.50, and 2.00 ct. A 0.90 ct stone can cost 15–20% less than a 1.00 ct of identical quality — with barely a millimetre difference in appearance.
04
Let the setting do some work.
Halo settings make a centre stone appear larger. Bezels conceal edge inclusions. Yellow gold neutralises warm tones. The right mount expands your effective budget by hundreds of euros.
05
Always buy certified.
Independent grading reports are the difference between certainty and guesswork. Every AZENA diamond is IGI, GIA, or GCAL certified — with the report available before you buy.
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Still deciding?
Our gemologists can guide you through every spec on every stone in our catalogue. No pressure, no hard sell — just honest advice from people who know diamonds.
AZENA Gemstones
Now you know what to look for. Go find yours.
Over 12,000 certified diamonds, fully filterable by every specification — delivered from EU stock with overnight shipping and expert guidance at every step.