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Diamond Grading

The full 4Cs — Cut, Color, Clarity, and Carat — plus fluorescence, proportions, and lab-grown detection. Independent, signed, and verifiable online.

Diamond value is concentrated in four measurable characteristics. Our reports document each on internationally recognized scales, with plotted inclusion mapping, proportion measurements, and explicit natural-versus-lab-grown determination.

The 4Cs

Four characteristics, four scales

Cut

How well the stone is proportioned and finished. Cut governs the brilliance, fire, and scintillation you actually see.

Color

For colorless diamonds, graded D (colorless) through Z (light yellow). Less body color = higher grade.

Clarity

The presence (or absence) of inclusions and surface blemishes. Graded under 10x magnification.

Carat

Weight, measured to two decimal places. 1 carat = 0.2 grams. Doubled weight is far more than doubled price.

Color

The D–Z color scale

Colorless diamonds are graded from D (perfectly colorless) down to Z (light yellow or brown). The differences are subtle and viewed against master stones in controlled light.

Diamond Color Scale (D–Z)ColorlessNear ColorlessFaintVery LightLightDEFGHIJKLMNOPQRSTUVWXYZTypical retail range (D–I)Grades compare a face-down diamond to GIA master stones under controlled D65 lighting.
GIA diamond color scale D–Z, grouped from colorless to light yellow.

What the bands mean

  • D–F (Colorless) — virtually no body color; the rarest and most expensive grades.
  • G–J (Near Colorless) — color noticeable only to a trained eye, especially when set in white metal. Strong value segment.
  • K–M (Faint) — faint yellow tint detectable face-up. Often set in yellow gold which masks the tint.
  • N–Z (Very Light to Light) — visible body color. Typically not used in high-jewelry.

Past Z, diamonds enter the "fancy color" range and are graded on an entirely separate scale (Fancy Light through Fancy Vivid).

Clarity

FL through I3 — the 11-grade clarity scale

Clarity is the assessment of internal inclusions and external blemishes at 10x magnification. Most clarity features are invisible to the unaided eye until SI2 and below.

Diamond Clarity ScaleFlawlessInternally FlawlessVery Very Slightly IncludedVery Slightly IncludedSlightly IncludedIncludedFLIFVVS1VVS2VS1VS2SI1SI2I1I2I3CleanerMore inclusions
Eleven GIA clarity grades, illustrated with representative inclusion patterns at 10x.
  • FL — Flawless: no inclusions or blemishes visible at 10x. Extremely rare.
  • IF — Internally Flawless: no inclusions at 10x; minor surface blemishes only.
  • VVS1 / VVS2 — Very, Very Slightly Included: inclusions extremely difficult to see at 10x.
  • VS1 / VS2 — Very Slightly Included: minor inclusions visible at 10x but typically not eye-visible.
  • SI1 / SI2 — Slightly Included: noticeable at 10x; SI2 may be eye-visible.
  • I1 / I2 / I3 — Included: obvious inclusions, often affecting transparency or durability.
Cut

Cut grade — the C that controls how a diamond actually looks

A poorly cut D-Flawless diamond can appear duller than a well-cut H-SI2. Cut grade measures how facet angles and proportions interact with light to produce brilliance, fire, and scintillation.

Diamond Cut GradesExcellentVery GoodGoodFairPoorLIGHT RETURN — better proportions → more brillianceCut grade is a function of proportions, symmetry, and polish — not size.
Round-brilliant cut grades from Excellent to Poor — better proportions return more light.
  • Excellent — facets aligned to return maximum light. Highest brilliance and fire.
  • Very Good — slight deviations from ideal; visually very close to Excellent.
  • Good — noticeable proportions deviation; light return reduced.
  • Fair / Poor — significant proportion or symmetry issues. Light leaks out the bottom or sides.

Cut grade applies primarily to round brilliants where the science is best established. Fancy shapes (princess, oval, cushion, etc.) use simplified cut descriptions because their geometry varies more.

Proportions

The geometry behind the grade

Cut grade is the rollup; proportions are the actual measurements. Our report documents each one.

Diamond Proportions Cross-SectionTable %Crown angleslope of crown facetsCrownheightGirdle thicknessedge between crown & pavilionPavilion angleslope from girdle to culetPaviliondepthCuletpoint at the base (ideally none/very small)Totaldepth %Proportions are measured as percentages of the average girdle diameter.
Cross-section showing the proportional landmarks measured during diamond cut grading.
  • Table % — the flat top facet as a percentage of total diameter. Typical 53–58% for round brilliants.
  • Total Depth % — total height as a percentage of diameter. Typical 59–63%.
  • Crown Angle — angle of the upper facets above the girdle. Typical 32–36°.
  • Pavilion Angle — angle of the lower facets below the girdle. Critical for light return; typical 40.6–41.8°.
  • Girdle Thickness — Thin / Medium / Slightly Thick / Thick / Very Thick.
  • Culet — the bottom point. None (preferred), Very Small, Small, Medium, Large.
Fluorescence

When the diamond glows under UV

Approximately one-third of natural diamonds fluoresce under long-wave UV light. We grade fluorescence on five levels: None, Faint, Medium, Strong, Very Strong. Most common color is blue; rare colors include yellow, white, and orange.

Does fluorescence affect value? Light fluorescence is generally neutral. Strong or Very Strong blue fluorescence in higher color grades (D-F) is sometimes considered a negative because in rare cases it produces a milky or hazy appearance in sunlight. In lower color grades (I-M), strong blue fluorescence can improve apparent color by masking the yellow tint.

Fluorescence is also a key signal in distinguishing natural from lab-grown diamonds — the patterns differ characteristically.

Authenticity

Natural vs lab-grown (HPHT, CVD)

Lab-grown diamonds are real diamonds — same chemistry, same hardness. They are grown in weeks rather than mined over geological timescales. Every GSR diamond report makes the natural / lab-grown determination explicit.

How we identify lab-grown

  • UV fluorescence patterns — natural diamonds show blue dominantly; CVD-grown often shows orange or red phosphorescence after UV exposure.
  • Spectroscopy — UV-Vis-NIR absorption signatures (Type IIa, Type IaB, Type IIb) classify diamonds into natural vs synthetic populations.
  • FTIR — hydrogen-related defects in CVD diamonds, nitrogen aggregation in natural diamonds — both are distinguishable in IR spectra.
  • Growth features — CVD diamonds may show plate-like growth patterns under specific imaging; natural diamonds show varied geological inclusions.
  • DiamondView / phosphorescence imaging — when available, growth-zone imaging is decisive.
Common questions

Diamond grading FAQ

What's the difference between Excellent and Ideal cut?

GIA uses Excellent as the top grade; AGS uses Ideal (0). They are broadly equivalent at the top of the scale, though AGS Ideal is defined slightly more strictly. The visual difference between top-tier Excellent and Ideal stones is generally not detectable to the naked eye.

Does fluorescence affect a diamond's value?

It depends on intensity and color grade. Strong/Very Strong blue fluorescence in D-F diamonds is sometimes discounted because of rare hazing effects. Medium and below typically has no value impact. In K-M, fluorescence can actually improve apparent whiteness. The cert reports fluorescence so you can decide.

How do you tell a natural diamond from a lab-grown one?

Several methods, used in combination: UV fluorescence patterns, UV-Vis-NIR spectroscopy, FTIR signatures, and growth-zone imaging where available. Modern HPHT and CVD synthetics are excellent quality and the detection is purely spectroscopic — visible inspection is not reliable.

Is a GIA report enough, or do I need a separate appraisal?

A grading report (from GIA, GSR, or others) describes what the stone is. An appraisal applies a monetary value based on current market conditions, suitable for insurance scheduling. Insurance companies typically require both — the grading report is the technical foundation, the appraisal is the value declaration. Learn about appraisals.

Why are color grades subjective?

Color grading is comparative — each stone is graded against a set of master stones in controlled lighting. Two well-trained gemologists should reach the same grade, but the difference between adjacent grades (G vs H, for example) is genuinely subtle. We document our methodology so buyers can interpret the grade with confidence.

Can a diamond be re-graded?

Yes. Diamonds can be resubmitted at any time — sometimes a re-cut produces an upgrade. Re-grading is also useful if a cert is decades old or from an unknown lab. We issue a fresh signed report with a new cert number.

Why does carat weight have such an outsize price impact?

Large diamonds are exponentially rarer than small ones. A 1ct is usually priced far more than 2× a 0.5ct of the same color/clarity. Prices also tend to step up at round-number weights (0.50, 1.00, 2.00ct) due to market psychology.

What is plotted inclusion mapping?

A diagrammatic top-and-side-view of the diamond showing the location and type of each significant inclusion. It functions as the stone's fingerprint — useful for identifying a specific diamond and for verifying that a stone matches its certificate.

Have a diamond to grade?

Submit a loose diamond and we'll return a full 4Cs report.

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Need a valuation too?

Combine grading with a replacement-value appraisal for insurance.

See Appraisal Services