The four characteristics that determine a diamond's quality, value, and beauty — explained by our in-house specialists.
When buying a diamond, you'll encounter four universal quality characteristics: cut, colour, clarity, and carat weight. Known as the 4Cs, this framework was developed by the Gemological Institute of America (GIA) in the 1940s and is used by every grading laboratory, jeweller, and retailer worldwide.
Understanding the 4Cs gives you the language to compare diamonds confidently and the knowledge to decide where your budget is best spent. Not every grade carries equal weight — and knowing which qualities matter most to you is the difference between a good diamond and the right one.
Cut
Of all four characteristics, cut has the greatest impact on how a diamond actually looks. It refers not to the shape of the stone, but to the precision of its faceting — the angles, proportions, symmetry, and finish that determine how light moves through it.
A well-cut diamond captures light and reflects it back through the top of the stone, creating three visual effects: brilliance (the return of white light), fire (the dispersion of light into colour), and scintillation (the sparkle as the stone moves). A poorly cut diamond — even one with excellent colour and clarity — will look flat and lifeless.
Cut is graded Excellent, Very Good, Good, Fair, and Poor. We recommend prioritising Excellent or Very Good cut above all other grades. The difference is visible to the naked eye and no amount of colour or clarity compensates for it.
Colour
Diamond colour is graded on a scale from D (completely colourless) to Z (light yellow or brown tint). The scale was established by GIA and is the global standard used by all reputable grading laboratories.
Colourless diamonds in the D–F range are the rarest and most valuable. However, the difference between adjacent grades is extremely subtle — often invisible to the naked eye, particularly once a diamond is set in a ring. Where colour becomes noticeable depends on the diamond shape, the metal it is set in, and lighting conditions.
As a general guide:
- D–F — Colourless. The highest grades. Recommended for platinum or white gold settings.
- G–J — Near colourless. Excellent value. Any warmth is virtually undetectable once set, particularly in yellow or rose gold.
- K–M — Faint colour. Visible to a trained eye. Better suited to vintage or warm-toned settings.
For most clients, G or H colour offers the best balance of quality and value. The stone reads as white to the naked eye, and the saving versus D–F grades is significant.
White Gold or Platinum
Prioritise D–H Colour
Cool metal tones contrast against any warmth in the diamond, making colour more visible. Staying within D–H ensures the stone reads as white against the setting.
- Colour more visible in cool metals
- D–F for the purest white look
- G–H offer excellent value
Yellow or Rose Gold
G–J Works Beautifully
Warmer metals complement a slightly warmer diamond — and can even enhance it. You can often go a grade or two lower with no visible difference.
- Warm tones complement the metal
- J colour can appear white when set
- Meaningful budget saving available
Clarity
Clarity describes the presence of inclusions (internal characteristics) and blemishes (surface characteristics) within a diamond. Almost all diamonds contain some degree of natural imperfection formed during crystallisation deep within the earth — these are what make each stone unique.
Clarity is graded on the following scale:
- FL / IF — Flawless / Internally Flawless. No inclusions under 10x magnification. Extremely rare.
- VVS1 / VVS2 — Very Very Slightly Included. Minute inclusions, extremely difficult to detect under magnification.
- VS1 / VS2 — Very Slightly Included. Minor inclusions visible under magnification but not to the naked eye.
- SI1 / SI2 — Slightly Included. Inclusions noticeable under magnification. SI1 is often eye-clean; SI2 should be reviewed carefully.
- I1 / I2 / I3 — Included. Inclusions visible to the naked eye. We do not recommend these grades for engagement rings.
The most important question to ask about any diamond is whether it is eye-clean — meaning no inclusions are visible without magnification at normal viewing distance. For most shapes, VS1 or VS2 offers excellent value while remaining completely eye-clean. SI1 can also be eye-clean, but this must be verified stone by stone.
Not Sure Which Grades Are Right for You?
Our specialists can walk you through specific stones and help you find the best balance for your budget.
Carat
Carat is the unit of measurement for a diamond's weight. One carat equals 0.2 grams. The word derives from the carob seeds historically used to balance scales when weighing precious stones.
It is important to understand that carat measures weight, not size. Two diamonds of the same carat weight can appear noticeably different in size depending on how they are cut and what shape they are. A well-cut one-carat round brilliant will appear larger than a poorly cut one-carat stone because its proportions direct more weight to the visible face-up surface.
Carat weight has a significant effect on price. Diamonds are priced per carat, and that price per carat increases sharply at certain thresholds — particularly at 0.50ct, 1.00ct, 1.50ct, and 2.00ct. Choosing a diamond just below these thresholds, for example 0.90ct or 0.95ct, can represent a substantial saving with virtually no visible difference in size.
How the 4Cs Work Together
The 4Cs do not exist in isolation — the grades interact, and understanding these relationships is where the real value lies when buying a diamond.
The most effective approach is to prioritise cut above everything else, then allocate the remaining budget across colour, clarity, and carat based on your personal priorities. Someone who values a larger stone might accept a slightly lower colour or clarity grade. Someone who values purity might prioritise colour and clarity over size.
There is no single right answer. The best diamond is the one that makes the most of your budget for the qualities that matter most to you — and that is exactly what our specialists are here to help you work out.
The best diamond isn't the one with the highest grades across the board. It's the one that makes the most of your budget for the qualities that matter most to you.
JQ Diamonds, In-House Diamond Specialists
Diamond Certification
Every diamond sold at JQ Diamonds comes with a certificate from an independent grading laboratory — either the GIA (Gemological Institute of America) or the IGI (International Gemological Institute). These certificates confirm the 4C grades, measurements, fluorescence, and other characteristics of the stone, providing an independent guarantee of what you are buying.
GIA is widely considered the most conservative and consistent grading standard in the world and is the benchmark against which other laboratories are measured. IGI is increasingly trusted, particularly for lab-grown diamonds, and their grading is generally reliable and consistent.
We never sell uncertified diamonds for engagement rings. The certificate is your assurance that the grades on paper match the stone in the setting.
