Natural Diamonds:
The Complete Guide
A natural diamond is the only thing on earth that began forming before life existed. Understanding how diamonds are graded — and what really matters when choosing one for a bespoke engagement ring — will help you make a decision you'll be proud of forever.
A 3-Billion-Year
Story
Natural diamonds are formed 150–200 kilometres beneath the earth's surface in the upper mantle — the layer of superheated rock sitting below the earth's crust. Under temperatures of 900–1,300°C and pressures exceeding 45,000 atmospheres, carbon atoms bond into an extraordinarily stable crystal lattice structure: the hardest natural material on earth.
This process takes between one billion and three billion years — meaning most of the diamonds in existence began forming before complex life appeared on this planet.
Diamonds are carried to the surface by deep volcanic eruptions called kimberlite pipes — events so ancient and powerful that none have occurred in recorded human history. This is why natural diamonds are genuinely, geologically finite. They cannot be replenished.
The 4Cs of Diamond Quality
GIA created the 4Cs — Cut, Colour, Clarity, and Carat Weight — as a universal method for establishing the quality of any diamond, anywhere in the world. Before the 4Cs, there was no common language for diamond quality. Today, these four measures appear on every GIA certificate and are the foundation of every diamond purchase.
Cut
Determines brilliance, fire and scintillation. The only C that is entirely the result of human skill. An Excellent cut transforms even a modest stone.
Colour
Graded D (perfectly colourless) to Z (light yellow). D–F are colourless; G–J are near-colourless and appear white to the naked eye in most settings.
Clarity
Measures inclusions (internal) and blemishes (external) using 10× magnification. VS1–VS2 are eye-clean. FL–IF are extremely rare.
Carat
A measure of weight — 1 carat = 0.200 grams. A well-cut 0.90ct can appear larger than a poorly-cut 1.00ct stone. Weight does not equal size.
Diamond Cut: Why It Matters Most
Of the 4Cs of diamond quality, a diamond's cut is said to have the greatest impact on a stone's beauty. An expertly cut diamond will appear brilliant even if it has lower colour and clarity grades, while a poorly cut diamond — even one with top colour and clarity — will look dull.
Excellent
Maximum brilliance, fire, and scintillation. Light is reflected efficiently throughout the stone. The pinnacle of cut craftsmanship. Always our first recommendation.
Very Good
Nearly as brilliant as Excellent. Slight differences in light performance that are virtually undetectable. Outstanding value.
Good
Reflects most light. Some light escapes through the bottom or sides. Acceptable for budget-conscious buyers.
Fair
Significant light leakage. The diamond appears noticeably less brilliant. We do not recommend this grade for engagement rings.
Poor
Light escapes from multiple angles. The diamond looks dull and lifeless. Avoid for any fine jewellery purpose.
What Determines a Cut Grade?
Brilliance
The total light reflected from a diamond — internal and external. Maximum brilliance means no light leaks through the base or sides.
Fire
The dispersion of light into the colours of the spectrum. A well-cut diamond shows rainbow flashes of colour.
Scintillation
The sparkle produced when a diamond, the observer, or the light source moves. Determined by the pattern of light and dark areas.
Purpose Driven Diamonds recommendation: Always prioritise an Excellent or Very Good cut. We will not set a stone below Very Good cut in any bespoke commission. The cut is the only C that is entirely in human hands — and it is where craft truly shows.
Diamond Colour: D to Z Explained
The GIA colour scale measures the absence of colour in a diamond. A chemically pure, structurally perfect natural diamond has no hue — like a drop of pure water. The scale runs from D (colourless, the finest) to Z (light yellow or brown). Colour is graded face-down by trained graders in standardised lighting against masterstones.
Colour & Metal Pairing
In platinum or white gold settings, D–H colour is ideal. The cool metal makes any warmth in the stone visible.
In yellow or rose gold settings, H–J colour can appear equally white — the warm metal masks any slight tint in the diamond. This is where the best value lives.
Colour & Diamond Shape
Round brilliant cuts disperse colour well. A G–H grade appears colourless to the eye in most settings.
Step cuts (emerald, Asscher) show colour more readily due to their large open facets. We recommend F–G for these shapes for the clearest white appearance.
Diamond Clarity: What's Inside Matters Less Than You Think
A diamond's clarity — its relative lack of inclusions and blemishes — is graded on a scale ranging from Flawless to Included. The size, number, position, relief, and type of inclusion or blemish present, and how easily they can be seen at 10× magnification, determine a diamond's clarity grade.
No inclusions or blemishes at 10×.
Only blemishes visible at 10×.
Inclusions very difficult to see at 10×.
Inclusions minor, ranging from difficult to somewhat easy to see at 10×. Eye-clean.
Inclusions noticeable at 10×. May be eye-clean in SI1 with brilliant cuts.
Inclusions obvious at 10×. May affect transparency.
Inclusions easily visible. Durability may be affected.
Inclusions very obvious. We do not recommend I-grade stones.
For Brilliant Cuts (Round, Oval, Cushion)
The best clarity for an engagement ring is usually VS2 or SI1 — these grades appear clean to the naked eye, deliver excellent sparkle, and offer strong value compared to higher grades. The facet pattern of brilliant cuts disperses light in a way that masks inclusions beautifully.
For Step Cuts (Emerald, Asscher)
For step-cut shapes like emerald or Asscher, VS1 provides added reassurance since these cuts reveal inclusions more easily. The large open table facet of a step-cut acts almost like a window into the stone.
Diamond Carat: Size Is Not Everything
Carat is a unit of weight — not size. One carat equals 0.200 grams, divided into 100 points (so a 0.75ct diamond = 75 points). Crucially, a well-cut 0.90ct diamond will appear larger and more brilliant than a poorly-cut 1.00ct stone. Carat weight alone is the least useful guide to a diamond's visual impact.
Approximate Face-Up Diameter — Round Brilliant Cut
Sizes are approximate and vary with cut quality. A shallower cut may show a larger face-up diameter at the same carat weight.
Our advice: Consider buying a 0.90ct or 0.95ct rather than a 1.00ct stone. You save significantly — carat prices jump at whole and half-carat thresholds — and the visual difference is imperceptible in a well-designed setting. This is one of the most effective ways to invest more budget in cut quality and metal choice.
The GIA Diamond
Grading Report
The GIA Diamond Grading Report uses universally accepted GIA standards to determine a natural diamond's shape, colour, clarity, cut, and carat weight — as well as proportions, finish, and treatments. It also includes a plotted diagram which maps the diamond, identifying its unique characteristics.
The report number is laser-inscribed on the girdle of the diamond — invisible to the naked eye, verifiable under magnification. Every GIA report can be verified instantly at gia.edu/report-check using the unique report number.
Multiple GIA graders independently evaluate each diamond and use proprietary grading technology. The grade is not determined until there is consensus — additional graders may be brought in until a determination can be made.
"A GIA certificate is not just a piece of paper. It is an independent, unbiased, verifiable record of exactly what you are buying. Never purchase a significant diamond without one."
What a GIA Report Includes
Unique identifier laser-inscribed on the diamond's girdle. Verify instantly at gia.edu/report-check.
e.g. Round Brilliant, Oval Modified Brilliant, Emerald.
Length × Width × Depth in millimetres, to the hundredth.
Weighed to the fifth decimal place. Reported to the nearest hundredth.
Graded face-down under standardised light, compared to masterstones.
Assessed under 10× magnification by multiple independent graders.
For round brilliant diamonds. Five-point scale: Excellent to Poor.
Each graded Excellent, Very Good, Good, Fair, or Poor.
None, Faint, Medium, Strong, or Very Strong. Blue fluorescence is most common.
Diagram mapping inclusions and blemishes with key symbols.
Cross-section showing all proportions with measurements.
Any additional observations, including treatments or unusual characteristics.
GIA Report Types for Natural Diamonds
Full 4Cs + plotted diagram. Standard for important stones over 1ct.
Full 4Cs without plotted diagram. For 0.15–1.99ct stones.
Full 4Cs + verified country of origin. Our recommendation for ethically sourced stones.
Full 4Cs + face-up image. Digital format for 0.15–2.99ct stones.
Diamond Shapes for Engagement Rings
Shape is the outline of the diamond as viewed face-up. It is a matter of personal taste — but different shapes suit different settings, finger types, and lifestyles. For bespoke engagement rings, shape is often the first decision.
Round Brilliant
The most popular shape for engagement rings worldwide. 57–58 facets designed for maximum brilliance. The only shape with a GIA cut grade. Timeless, versatile, and the brightest performer.
Oval
A modified brilliant that appears larger face-up than a round of the same carat weight. Elongates the finger. Currently among the most requested shapes for bespoke engagement rings.
Cushion
A square or rectangular shape with rounded corners and large, open facets. Romantic and vintage in character. Excellent at displaying a diamond's fire and colour.
Emerald
A rectangular step-cut with a large open table. Offers a clean, architectural elegance. Shows colour and clarity more readily — VS1 clarity and G+ colour recommended.
Princess
A square brilliant cut. Modern, geometric, and angular. Second most popular for engagement rings. Works beautifully in four-claw or bezel settings.
Pear
A teardrop shape combining round and marquise. Worn with the point toward the fingernail. Elongates the hand and finger. Unique and distinctive.
Asscher
A square step-cut with a very high crown. Creates a striking stepped-reflection effect with a deep, architectural clarity. Requires VS1+ clarity for the same reasons as emerald. Art Deco in character.
Marquise
An elongated shape with pointed ends. The largest face-up surface area of any shape at a given carat weight. Dramatic and unusual. Requires attention to symmetry.
Choosing a Diamond for Your
Bespoke Engagement Ring
Our Priority Order
Cut
Always Excellent or Very Good. This single decision determines more than any other.
Shape
Choose what moves you — this is personal and permanent.
Colour
G–H for platinum/white gold. H–J for yellow/rose gold. Eye-clean is the target.
Carat
Choose the size that suits the design and the finger. Consider just below round numbers.
Clarity
VS2 or VS1 for brilliant cuts. VS1 for step cuts. Eye-clean is the standard.
What We Do Differently
We source responsibly
Every natural diamond we set comes with verified country of origin documentation. We work only with suppliers who demonstrate responsible mining practices.
We show you the certificate first
Before you make any decision, we walk through the GIA report with you in detail — every measurement, every grade, every characteristic. You make an informed choice.
We never upsell on carat
We will always recommend the stone that best serves your design — not the largest stone that fits your budget. A beautifully cut 0.90ct serves a bespoke ring better than a poorly-cut 1.20ct.
We check every stone personally
Every diamond we use in a bespoke commission is assessed by our sourcing team under magnification before we accept it. The certificate tells us what it is. Our assessment confirms how it performs.
We document the journey
Your completed piece comes with a full provenance file — the GIA certificate, origin documentation, and a record of the bespoke design process. Yours to keep.
Ready to Choose Your
Natural Diamond?
Our team will guide you through every option at your free consultation. We bring the GIA reports, the stones, and the knowledge. You bring the vision. Together we'll find the right diamond for your story.
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