Diamond glossary — Professional B2B lexicon
This glossary brings together all essential definitions for jewelry, goldsmithing and diamond trading professionals. From the 4Cs (carat, color, clarity, cut) to GIA certification grades, diamond cuts, market terms like the Rapaport price list, and new traceability technologies like TRACR.
- Asscher cut
Square step-cut with cut corners, created by the Asscher brothers in 1902. Its rectangular step facets create a characteristic depth effect often called a 'hall of mirrors'. Highly prized in Art Deco jewelry.
- AGS Ideal (cut grade)
Cut grade 0 from the American Gem Society (AGS), equivalent to the highest optical performance level. The AGS developed a 3D proportion evaluation method (Table, Pavilion, Crown) identifying Round Brilliant diamonds with optimal light management. Pimento Diamonds uses the AGS table of 569 combinations to automatically assign the Signature Cut label.
- Diamond bourse
Official marketplace where rough and polished diamonds are traded between professionals. Antwerp (Belgium) hosts four bourses and remains the world diamond capital, handling over 80% of global rough diamond trade.
- Bow-tie effect
Dark bow-tie-shaped optical defect visible at the center of elongated fancy cuts (oval, pear, marquise, elongated cushion). Caused by a pavilion angle that is too open or closed on the long axis of the stone, creating a central shadow zone. A pronounced bow-tie significantly reduces a diamond's value and appeal. It is not graded by the GIA: its significance must be judged from HD photos and videos before purchase.
- Carat (weight)
Unit of measurement for the weight of precious stones. 1 carat = 0.20 grams. The carat is one of the 4Cs that determine a diamond's value. At equal quality, the price per carat increases exponentially with weight.
- Calibrated diamond
Diamond cut to standardized dimensions (in millimeters), enabling use in paving, rows or parures without individual adjustment. Essential for mass-set jewelry. Pimento Diamonds maintains a permanent calibrated stock.
- Gemological certificate
Official document issued by an independent laboratory (GIA, IGI, HRD) certifying a diamond's precise characteristics: weight, color, clarity, cut, proportions, fluorescence. It is the diamond's 'identity card', essential for any serious B2B transaction.
- Clarity
One of the 4Cs, clarity measures the absence of inclusions (internal flaws) and blemishes (surface flaws) in a diamond. The GIA scale ranges from FL (Flawless) to I3. The purer the diamond, the rarer and more valuable it is.
- Color
One of the 4Cs. For white diamonds, the GIA scale runs from D (completely colorless, rarest) to Z (perceptible yellow tint). Each grade below D represents a slight yellow or brown tint. D-F are 'colorless', G-J 'near colorless'.
- Color D
The highest color grade on the GIA scale. A D diamond is completely colorless, even when compared to other D diamonds under controlled light. Represents less than 1% of world production. Combined with FL or IF clarity, it is the absolute pinnacle of white diamonds.
- Color E
Second GIA color grade, virtually impossible to distinguish from D without laboratory equipment. A professional gemologist can only detect the difference in direct comparison under controlled light. Excellent rarity-quality-value ratio for high jewelry.
- Color F
Third grade on the GIA scale, still in the 'colorless' category. The slight trace of color is only detectable by a qualified gemologist with direct comparison. Highly prized in fine jewelry for its excellent quality/price ratio compared to D-E grades.
- Color G
First grade in the GIA 'near colorless' category. The slight tint is almost impossible to detect with the naked eye and remains invisible once set in jewelry. Represents the best quality/value compromise for engagement rings and B2B jewelry.
- Color H
Fourth 'near colorless' grade on the GIA scale. A slight warm tint may be perceptible to the naked eye on an isolated diamond, but is practically invisible in jewelry. One of the most popular grades in mass jewelry and B2B retail thanks to its excellent quality/price ratio.
- Cushion cut
Cut with rounded outlines resembling a cushion, with large facets that maximize brilliance. Existing since the 19th century, it remains one of the most popular cuts in luxury jewelry. Available in square and elongated versions.
- Heart cut
Heart-shaped brilliant cut, the ultimate romantic symbol. Requires exceptional craftsmanship to achieve perfect symmetry. Cut quality is critical: an irregular or poorly proportioned heart loses its charm entirely. Popular for engagement rings and pendants.
- Cut
One of the 4Cs, often considered the most important. Cut determines how the diamond interacts with light — its brilliance, fire and scintillation. The GIA scale runs from Excellent to Poor. An Excellent cut maximizes perceived luminosity.
- D / IF / FL
The maximum quality combination: D color (absolutely colorless), IF clarity (Internally Flawless, no inclusions visible at ×10 magnification) or FL (Flawless, no defects at all). These diamonds represent less than 0.1% of world production and are intended for high jewelry.
- Natural diamond
Diamond formed naturally in the Earth's mantle under extreme conditions of pressure and temperature, billions of years ago. Brought to the surface by volcanic eruptions (kimberlites). To be distinguished from synthetic (lab-grown) diamonds produced in a laboratory.
- Emerald cut
Rectangular step-cut with cut corners. Its large parallel facets create an elegant 'mirror' effect rather than intense brilliance. This cut highlights the diamond's clarity and color — inclusions are more visible.
- Eye-clean
A diamond is called 'eye-clean' when no inclusions are visible to the naked eye at a standard distance of 25-30 cm. 'Eye-clean' is not an official GIA grade — it is a qualitative commercial assessment. A well-oriented SI1 is often eye-clean; VS2 is virtually always eye-clean. A crucial criterion in remote B2B sales, as it justifies purchase without prior physical examination.
- Fancy color diamond
Natural diamond with an intense color (intense yellow, pink, blue, green, red, orange…). Graded on a specific GIA scale from Faint to Fancy Vivid. Fancy Vivid diamonds are among the rarest and most precious in the world.
- Fisheye effect
Optical defect visible in Round Brilliant diamonds with an overly large table (>65%) or too flat a pavilion. The culet reflects through the table as a dark circle, reducing perceived brilliance. Pimento Signature Cut diamonds systematically avoid this effect through strict AGS proportion selection.
- FL — Flawless
Highest GIA clarity grade: no inclusions or blemishes visible under ×10 magnification by a qualified gemologist. Extremely rare — less than 1% of GIA-certified diamonds achieve this grade. Combined with D color, it is the perfect diamond.
- Fluorescence
A diamond's property to emit a visible glow (often blue) when exposed to ultraviolet (UV) rays. Measured from None to Very Strong by GIA. Blue fluorescence can improve the appearance of a yellow-tinted diamond, but slightly decrease the value of D-F stones.
- GIA — Gemological Institute of America
World's leading gemological laboratory, founded in 1931 in the United States. GIA created the 4C scale and D-to-Z color standard. Its certificates are recognized and respected worldwide. It is the reference standard for B2B diamond trading.
- Girdle
The peripheral band of the diamond, at the junction between the crown (upper part) and pavilion (lower part). Girdle thickness is noted on the GIA certificate, from Extremely Thin to Extremely Thick. An extremely thin girdle can make the diamond vulnerable to chipping.
- HRD — Hoge Raad voor Diamant
Belgian gemological laboratory founded in Antwerp in 1973. One of the three major global laboratories alongside GIA and IGI. HRD certificates are particularly recognized in Europe. Antwerp, world diamond capital, houses HRD headquarters.
- IF — Internally Flawless
Second GIA clarity grade, just below FL. An IF diamond shows no inclusions visible at ×10 magnification, but may have very slight blemishes (surface defects). Extremely rare and prized, it is often the target grade for high-end jewelers.
- IGI — International Gemological Institute
Gemological laboratory founded in Antwerp in 1975, with labs in 20 countries. IGI has become the leading certifier for synthetic (lab-grown) diamonds. For natural diamonds, its grades are generally slightly more generous than GIA's.
- Inclusion
Internal imperfection in a diamond, naturally present during its formation: mineral crystals, feathers (fractures), clouds (groups of micro-crystals), needles, cavities… Inclusions give each diamond a unique 'fingerprint'. Their number, size and position determine the clarity grade.
- Kimberley Process
International certification system created in 2003 to prevent trade in 'conflict diamonds' (diamonds financing armed conflicts). Adopted by 85 countries representing 99.8% of the global rough diamond trade. Pimento Diamonds ensures all its suppliers comply.
- Lab-grown diamond
Diamond produced in a laboratory by two methods: HPHT (High Pressure High Temperature) or CVD (Chemical Vapour Deposition). Chemically identical to natural diamond, but without geological rarity. Its price has fallen 90% in 10 years. Pimento Diamonds specializes in natural diamonds.
- Marquise cut
Elongated navette-shaped cut with two pointed ends. Creates an optical illusion that elongates the finger. Maximizes visible size — a marquise diamond appears larger than a round of the same carat. Requires special attention to the bow-tie effect.
- Melee diamonds
Small diamonds under 0.20 carat (typically 0.01 to 0.18 ct) used for paving, wedding bands and pavé settings. Sold by lot according to diameter in millimeters. Pimento's calibrated diamonds are ideal for this use.
- Untreated
Diamond whose color or clarity has not undergone any artificial treatment (irradiation, HPHT, fracture filling, laser drilling). GIA, IGI and HRD certificates must mention any detected treatment. Pimento Diamonds only offers untreated natural diamonds.
- Nail head effect
Optical defect opposite to fisheye: it occurs when the pavilion angle is too steep (>41.5°). The culet casts a dark spot-shaped shadow at the center of the table, resembling a nail head. This defect reduces brilliance and scintillation. Pimento Signature Cut proportions systematically exclude this overly deep pavilion zone.
- Oval cut
Elliptical brilliant cut, derived from the round brilliant. Like the marquise, it creates an illusion of finger elongation. Very trendy since 2015, the oval offers excellent brilliance-to-weight ratio. Watch for the bow-tie effect in narrow ovals.
- Pear cut
Hybrid cut combining the round brilliant and marquise: one rounded end and one point. Widely used for pendants and earrings. The point must be carefully protected by the setting to avoid chipping.
- Princess cut
Square cut with straight corners and brilliant facets on the crown. Second most popular cut after the round brilliant. Offers excellent brilliance at a generally lower price than a round of the same carat, as it preserves more rough material during cutting.
- Clarity (purity)
See 'Clarity'. The GIA scale: FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2, I3.
- Optical performance (cut)
Measure of a polished diamond's ability to manage light: brilliance (reflected white light), fire (dispersion of light into spectral colors), and scintillation (flashes during movement). Optical performance depends directly on cut proportions — table, pavilion angle, crown angle — and not solely on GIA grade. A GIA Triple Excellent diamond can have lower optical performance than an ungraded diamond if its proportions deviate from the AGS ideal zone.
Browse Signature Cut in stock · Pimento Signature Cut selection
- Polish
One of the three cut criteria graded by GIA in its cut report (along with cut and symmetry). It measures the surface quality of each facet. The GIA scale ranges from Excellent to Poor. Excellent polish guarantees facets free from micro-scratches, wheel burns, or polishing marks, which would reduce light transmission through the stone. Polish is part of the Triple Excellent prerequisite for Pimento Signature Cut diamonds.
- Radiant cut
Rectangular or square cut with cut corners, combining the brilliant facets of the round cut with the emerald silhouette. Offers intense brilliance while maintaining an elegant rectangular shape. Highly prized for modern solitaires and engagement rings.
- Rapaport price list
Weekly price list published by the Rapaport Diamond Corporation (founded 1978), the absolute reference of the world polished stone market. Expressed in USD per carat by shape, weight, color and clarity. Professional prices are expressed as a percentage discount from Rap.
- Round brilliant cut
The world's most popular cut, representing around 75% of diamond sales. Its 57 or 58 facets have been mathematically optimized to maximize brilliance, fire and scintillation. The round brilliant is the absolute reference for evaluating GIA cut quality.
- SI — Slightly Included
GIA clarity grade comprising SI1 and SI2. Inclusions are visible under ×10 magnification but may be difficult to see with the naked eye (SI1) or visible with careful inspection (SI2). Excellent value for everyday jewelry, often 'eye-clean' at SI1.
- Ethical sourcing
Sourcing natural diamonds with respect for human rights, the environment and international regulations (Kimberley Process, OECD). Pimento Diamonds commits to working only with certified suppliers who are transparent about the origin of their stones.
- Signature Cut (Pimento label)
Pimento Diamonds internal selection label identifying Round Brilliant diamonds whose proportions (Table, Pavilion, Crown) fall within the AGS Ideal (grade 0) or AGS Excellent (grade 1) zone. This label does not replace the GIA, IGI or HRD certificate — it adds an optical performance analysis layer. Triple EX (Excellent Cut + Excellent Symmetry + Excellent Polish) is a prerequisite. Calculated automatically via a database of 569 AGS proportion combinations.
- Symmetry
One of the three cut criteria graded by GIA alongside cut and polish. Symmetry measures the geometric precision of facet placement and alignment — whether opposite facets are aligned, whether the culet is centered, whether the table is properly positioned. The GIA scale ranges from Excellent to Poor. Poor symmetry creates an irregular light pattern visible to the naked eye. Excellent symmetry is mandatory for a diamond to qualify for Pimento Signature Cut.
- Table facet
The largest facet of the diamond, flat, at the top of the crown. Its percentage (ratio between table width and total diamond diameter) is a key parameter of cut quality. For a GIA Excellent round brilliant, the table is typically between 54% and 60%.
- TRACR (blockchain traceability)
Blockchain traceability platform developed by De Beers, allowing tracking of a diamond's journey from mine to jewelry store. Each TRACR diamond receives a unique digital identifier verified by 3D optical measurements. Pimento Diamonds is one of the few B2B suppliers to offer TRACR diamonds in Europe.
- Triple Excellent (GIA)
The maximum grade awarded by GIA when a diamond scores Excellent in all three cut criteria: Cut, Symmetry, and Polish — abbreviated as 3EX or Triple EX. Approximately 15 to 20% of GIA-certified Round Brilliants reach this grade. Important: two Triple Excellent diamonds can have very different optical performances depending on their exact proportions. This grade is a necessary but not sufficient condition to reach AGS Ideal. Pimento's Signature Cut program begins where Triple Excellent leaves off.
- VS — Very Slightly Included
GIA clarity grade comprising VS1 and VS2. Inclusions are minor and difficult to see under ×10 magnification. To the naked eye, these diamonds are almost always 'eye-clean'. Excellent quality-to-price ratio for engagement rings and B2B jewelry.
- VVS — Very Very Slightly Included
GIA clarity grade comprising VVS1 and VVS2. Inclusions are extremely difficult to see even for a qualified gemologist under ×10 magnification. To the naked eye, these diamonds are absolutely perfect. Very popular in the premium segment of luxury jewelry.