Diamond glossary: 300+ terms defined

Surface wear on a diamond facet, appearing as a white or frosted edge at the facet junction. Caused by contact with harder materials (other diamonds) or by poor handling. Noted in GIA clarity grading as a surface characteristic.

A US-based gemological organisation that operates the AGS Laboratories, one of the major diamond grading laboratories. AGS uses a 0-to-10 grading scale (0 is best) rather than the GIA word scale. Known for rigorous cut grading methodology.

A diamond found in secondary deposits, transported by water from its original kimberlite source. Alluvial diamonds are found in riverbeds, coastal deposits, and marine mining zones. They are often rounded from water transport and may be of higher average quality than primary mine output because lower-quality stones broke down during transport. See: Alluvial deposits.

A square step-cut diamond with an octagonal outline, developed by the Asscher Brothers of Amsterdam in 1902. Characterised by deeply cut corners, high crown, and a distinctive "hall of mirrors" visual effect. Associated with Art Deco jewellery. See: Asscher cut guide.

Blue fluorescence in a diamond, the most common fluorescence colour. Caused by the N3 defect centre (three nitrogen atoms around a vacancy) absorbing UV radiation and emitting blue visible light. Graded by GIA as None, Faint, Medium, Strong, or Very Strong.

A small rectangular step-cut diamond, typically used as an accent stone in jewellery settings. The baguette cut was standardised during the Art Deco period (1920s) specifically for geometric settings. A tapered baguette has one end narrower than the other, for use in settings that converge toward a centre stone.

A ring setting in which a rim of metal completely surrounds the girdle of the diamond, holding it securely. The bezel is the most protective setting for active wearers. A partial bezel (also called an east-west bezel) covers only two sides of the stone. See: Bezel settings.

A dark bowtie-shaped shadow visible across the centre of some fancy-cut diamonds, particularly ovals, marquises, and pear shapes. Caused by light escaping through the pavilion rather than reflecting back to the viewer in that area. The severity of the bowtie varies by stone and must be evaluated by viewing the specific stone, not from a certificate.

The white light returned from the interior of a diamond to the viewer's eye. Brilliance is produced by the reflection and refraction of light through the diamond's facets and is the primary component of a well-cut diamond's visual appeal. Distinct from fire (coloured light dispersion) and scintillation (sparkle on movement).

Any diamond cut with triangular and kite-shaped facets radiating from the centre, designed to maximise light return. The modern round brilliant has 58 facets in a specific arrangement optimised through the 20th century. Other brilliant-style cuts include oval, cushion (modified brilliant), and pear.

The process of shaping a rough diamond into a round outline by rotating two diamonds against each other on a lathe. The first major step in cutting a round brilliant after cleaving or sawing. The bruted stone (the "brute") has a rough girdle that is subsequently polished.

Gemstones cut to custom shapes to fit specific positions in a jewellery setting. Calibré cuts are characteristic of Art Deco and Edwardian jewellery, where geometric settings required precisely fitted rectangular, triangular, or other shaped stones. Fine calibré cutting is a mark of quality in period jewellery.

A provenance certification programme for diamonds mined in Canada, tracking stones from mine to polished with serial number documentation. Canada Mark diamonds carry a laser inscription and chain of custody documentation certifying Canadian origin. See: Ethical diamond sourcing.

The unit of weight for gemstones. One carat equals 0.20 grams or 200 milligrams. The word derives from the carob seed, historically used as a weight standard. Carat is a measurement of weight, not size; two diamonds of equal carat weight may have different face-up dimensions depending on their cut proportions. See: Carat guide.

A solitaire ring setting in which the shank rises toward the head in arching shapes resembling cathedral architecture, supporting the diamond at an elevated position. The cathedral profile adds height and visual presence to the ring and is associated with traditional and classic engagement ring styles.

A setting style in which diamonds are set in a row between two parallel metal rails (the "channel"), with the stones' girdles resting on ledges cut into the rails. Channel settings offer good protection to the stones (no prongs to catch or bend) and are commonly used in eternity bands and men's rings. Less easy to clean than prong settings.

A V-shaped or zigzag geometric pattern used in Art Deco jewellery design. A chevron-set ring or bracelet has stones arranged in alternating V formations, a characteristic motif of 1920s geometric jewellery. Also used in modern jewellery design as a stack ring pattern.

The World Jewellery Confederation (Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie). The international body that sets standards for the jewellery trade, including the Diamond Blue Book which defines grading terminology and disclosure requirements. See: CIBJO Diamond Blue Book.

One of the 4Cs. A measure of the extent to which a diamond is free from inclusions (internal characteristics) and blemishes (surface characteristics). GIA grades clarity on an 11-point scale from Flawless (FL) to Included (I3). See: Clarity guide.

A diamond's tendency to split along specific crystallographic planes (the octahedral cleavage planes) when struck with sufficient force in the correct direction. Diamond cutters exploit cleavage to split large rough crystals. Diamonds are the hardest natural material but are not indestructible; a sharp blow at the right angle can cleave a diamond cleanly.

A cluster of very small pinpoint inclusions in a diamond that appear as a hazy or milky area under magnification. Clouds may affect transparency and brilliance if large or heavily concentrated. A cloud noted on a GIA certificate is typically harmless unless the comments specifically note that it affects transparency.

A simple metal cup or collar setting that holds a gemstone from below and around the girdle. The traditional collet is a cylindrical or tapered metal band soldered to the ring shank. In antique jewellery, collets are often made in silver (silver-topped gold construction) for their better visual contrast with diamonds.

One of the 4Cs. GIA grades colour on a D (colourless) to Z (light yellow or brown) scale for white diamonds. D, E, F are colourless; G, H, I, J are near-colourless; K, L, M are faint yellow. Fancy colour diamonds (intense colours outside the normal colour range) are graded on a separate Fancy Colour scale. See: Colour guide.

A ring construction in which the inner surface of the band has a slightly curved (domed) profile, making the ring easier to put on and take off and more comfortable for all-day wear than a flat-sided band. Standard for men's wedding bands and recommended for any band above 4mm width.

The upper portion of a diamond, above the girdle. The crown includes the table facet (the flat top), the bezel facets, star facets, and upper girdle facets in a brilliant cut. Crown height and angle significantly affect the diamond's light performance and visual character.

A mineral crystal trapped inside a diamond during its formation. Crystal inclusions can be small diamonds within the diamond (a diamond crystal), garnets, olivine, or other minerals. On a GIA clarity plot, crystal inclusions are shown as specific symbols. They may appear as dark or light spots depending on their composition.

The bottom point or facet of a diamond. In modern round brilliants, the culet is a pointed apex with no facet (or a very small facet graded "None" to "Large" by GIA). In antique cuts (old mine, old European), the culet is a large flat facet visible as a circle when looking through the table from above a period-identifying characteristic.

A diamond cut with a square or rectangular outline with rounded corners and brilliant-style facets. The cushion cut evolved from the old mine cut and is one of the most popular fancy shapes for engagement rings. Available in modified cushion (with an extra row of facets producing a "crushed ice" appearance) and standard cushion. See: Cushion cut guide.

One of the two main methods for growing lab-grown diamonds. CVD grows diamond by introducing hydrocarbon gases into a chamber and activating them with microwaves or plasma, depositing carbon atom by atom onto a substrate. CVD produces Type IIa diamonds and contains a specific Si-V defect centre detectable by spectroscopy. See: CVD process.

The total depth of a diamond (from table to culet) expressed as a percentage of the average girdle diameter. For a round brilliant, the ideal depth percentage is approximately 59 to 63 percent. Stones outside this range may be too shallow (light leaks through the bottom) or too deep (light leaks through the sides), both reducing brilliance.

An instrument developed by De Beers that images the fluorescence pattern of a diamond under short-wave UV light, revealing the crystal growth structure. Used by GIA and other laboratories to distinguish natural from lab-grown diamonds and to identify certain treatments. HPHT synthetic diamonds show distinctive cubic growth sector patterns in DiamondView imaging.

The separation of white light into its spectral colours as it passes through a transparent material. Diamond has high dispersion (fire coefficient of 0.044), which produces the rainbow flashes visible in a well-cut stone. Dispersion is a property of the material; fire in a specific stone is determined by both the material's dispersion and the cut's geometry.

The marketing and distribution arm of De Beers that allocates rough diamonds to approved buyers (Sightholders). The DTC conducts periodic "Sights" (sales events) at which Sightholders receive parcels of rough diamonds at prices set by De Beers. See: Diamond trade structure.

A historical diamond cut style with 18 facets, a precursor to the full brilliant cut. The double cut has a table, a culet, and a single row of facets on both the crown and pavilion. Found in some antique jewellery from the 17th and 18th centuries.

A rectangular step-cut diamond with cropped corners, known for its "hall of mirrors" visual effect and architectural clarity. Emerald cuts require higher clarity than brilliant cuts because step-cut facets make inclusions more visible. Associated with Art Deco aesthetic and glamorous, unfussy sophistication. See: Emerald cut guide.

An informal term describing a diamond with no inclusions visible to the unaided eye when viewed face-up from a normal viewing distance (approximately 25 to 30 cm). Most VS1, VS2, and SI1 diamonds are eye-clean. SI2 and below may or may not be eye-clean depending on the specific stone. Eye-clean is a visual assessment, not a GIA grade.

The orientation of a diamond as it sits in a ring setting with the table pointing upward toward the viewer. Diamond grades (colour, clarity) and face-up size (the apparent size of the stone when viewed from above) are assessed face-up. A stone's face-up size may differ from what its carat weight implies depending on its proportions.

A flat, polished surface on a diamond. The arrangement, angles, and proportions of facets determine a diamond's light performance. A modern round brilliant has 58 facets: 33 on the crown and 25 on the pavilion (including the culet). Each facet must be precisely angled and polished to achieve the intended light interaction.

A certification standard for artisanal and small-scale gold mining administered by the Alliance for Responsible Mining (ARM). Fairmined certification verifies environmental, labour, and community standards and pays a premium to the mining community. Available in India but not widely stocked; requires specific supply chain relationships. See: Ethical custom jewellery.

A diamond whose colour is beyond the D-to-Z normal colour range: yellows, oranges, pinks, blues, greens, reds, and other vivid colours. Fancy colour diamonds are graded on a separate scale (Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep, Fancy Dark). The rarest and most valuable colours are red, green, and vivid blue. See: Fancy colour diamonds.

A small fracture or cleavage break in a diamond, appearing as a wispy, white, slightly translucent line under magnification. Feathers reaching the surface (surface-reaching feathers) represent a structural weakness and are more concerning than internal feathers. A large surface-reaching feather can compromise the stone's durability.

The coloured light flashes visible in a diamond, produced by the dispersion of white light into spectral colours as it passes through the stone. Fire is maximised by high crown angles, which increase the angle of light refraction. Antique cuts (old mine, old European) produce more visible fire than modern brilliants in warm incandescent light. See also: Dispersion.

The highest GIA clarity grade. A Flawless diamond has no inclusions or blemishes visible under 10x magnification to a trained grader. FL diamonds are extremely rare; GIA grades fewer than 1 percent of submitted diamonds as FL. The visual difference between FL and VS1 is not detectable by the unaided eye and rarely visible even under magnification.

The emission of visible light by a diamond when exposed to ultraviolet radiation. Most diamond fluorescence is blue, caused by the N3 defect centre. GIA grades fluorescence as None, Faint, Medium, Strong, or Very Strong. Strong fluorescence can cause a milky or hazy appearance in some diamonds under UV-rich light (natural daylight). See: Diamond science.

The four grading criteria used to assess diamond quality: Cut, Colour, Clarity, and Carat weight. The 4Cs framework was standardised by GIA and is now universally used in diamond grading and consumer communication. Cut is generally considered the most important C for a diamond's visual appearance. See: The complete 4Cs guide.

A clarity enhancement treatment in which a glass-like substance is injected into surface-reaching fractures in a diamond to make them less visible. Fracture filling is detectable by the "flash effect" (coloured flashes at the fracture under magnification) and by EDS spectroscopy. GIA does not grade fracture-filled diamonds. See: Clarity enhancement.

An analytical technique that measures which infrared wavelengths are absorbed by a diamond. FTIR identifies the diamond's type (Ia, IIa, IIb, Ib) through the nitrogen and boron absorption patterns it reveals. GIA uses FTIR as a standard tool for all diamonds it grades. See: Diamond science.

The world's foremost diamond grading laboratory and gemological education institution, founded in 1931. GIA invented the 4Cs grading framework and the International Diamond Grading System. GIA certificates are the gold standard for diamond grading internationally. See: GIA explained.

India's apex trade body for the gems and jewellery industry, established under the Ministry of Commerce. GJEPC promotes Indian gem and jewellery exports, maintains trade statistics, and sets industry guidelines including protocols for separation of natural and lab-grown diamonds in Surat's cutting factories.

The narrow edge of a diamond between the crown (upper portion) and pavilion (lower portion). The girdle is the widest part of the diamond in face-up view and is the reference for most diameter measurements. Girdle thickness is graded from Extremely Thin to Extremely Thick by GIA; Very Thin to Slightly Thick is the preferred range for round brilliants.

A diamond originating from the historic Golconda mining region in what is now Telangana, India. Golconda diamonds were the world's primary diamond source from antiquity through the 18th century and include many of the most famous diamonds in history (Koh-i-Noor, Hope Diamond, Regent). Golconda stones are typically Type IIa and often associated with exceptional clarity and colourlessness. See: Ancient India and Golconda.

Internal irregularities in a diamond's crystal structure caused by uneven growth. Graining can appear as faint lines, curves, or angular features under magnification. White graining is listed as a clarity characteristic; coloured graining may affect colour grade. Graining is a natural feature of diamond growth and is not a treatment or defect.

A stamped mark in metal certifying its purity and origin, applied by a government assay office. British hallmarks include the purity mark, assay office symbol, and date letter (allowing precise year of assay identification). Essential for authenticating antique British and European jewellery. See: Authentication guide.

A ring setting in which the centre diamond is surrounded by a ring of smaller diamonds, increasing the apparent size of the centre stone and adding sparkle. Halo settings require careful maintenance as the small pavé stones can loosen over time. Double halos use two concentric rings of smaller diamonds. See: Halo settings.

A modified brilliant cut in the shape of a heart, typically with 59 facets. One of the most technically demanding fancy shapes to cut because the symmetry must be perfect and the cleft at the top well-defined. Best viewed at 0.70 carats and above to be clearly legible as a heart shape. See: Heart diamond guide.

1. A method for growing lab-grown diamonds by simulating the Earth's mantle conditions in an industrial press. HPHT synthesis produces Type Ib diamonds with isolated nitrogen. 2. A diamond colour treatment applying extreme pressure and temperature to natural diamonds to modify their colour (typically decolourising brown Type IIa diamonds). See: HPHT growth and HPHT treatment.

The second-highest GIA clarity grade. An Internally Flawless diamond has no inclusions visible under 10x magnification but may have minor surface blemishes. IF diamonds are rare and command a premium over VS1 without any practical visual difference in a set ring.

A major diamond and gemstone grading laboratory founded in Antwerp in 1975 with locations in Antwerp, Mumbai, New York, and other cities. IGI is the primary grading laboratory for lab-grown diamonds globally and an important grading laboratory for the Indian diamond trade. GIA and IGI grades are generally similar but not always identical; for natural diamonds above 1 carat, GIA certification is the global standard. See: IGI explained.

An internal characteristic of a diamond formed during its crystallisation or subsequent geological events. Inclusions include crystals, feathers, clouds, needles, pinpoints, and other features. GIA clarity grading assesses inclusions on the basis of their size, position, nature, quantity, and effect on transparency. Most inclusions are inert and have no practical effect on the diamond's durability or beauty. See: Clarity guide.

A portion of the original rough diamond's surface that dips below the polished surface, typically at the girdle. An indented natural is a surface reaching feature that a cutter has intentionally left to preserve carat weight. It is noted on GIA certificates and maps as a surface characteristic.

A traditional Indian jewellery technique in which gemstones (typically uncut diamonds, rubies, and emeralds) are set directly into gold without a backing, with the gold worked around the stones. Jadau jewellery is associated with Rajasthani and Mughal jewellery traditions and represents some of the most technically accomplished traditional Indian jewellery craft. See: Antique Indian diamonds.

A traditional Indian earring style with a dome or bell-shaped drop, often set with gemstones including diamonds. Jhumkas are a staple of traditional Indian formal jewellery and appear in both plain gold and diamond-set versions. Diamond jhumkas typically feature pavé-set small diamonds on the dome and sometimes on the hook component.

A measure of gold purity, distinct from carat (diamond weight). 24 karat = pure gold. 18 karat (18kt or 750) = 75 percent gold. 14 karat (14kt or 585) = 58.5 percent gold. 22 karat (22kt or 916) = 91.6 percent gold (the most common purity for traditional Indian gold jewellery). Most diamond engagement rings use 18kt or platinum.

An international certification scheme established in 2003 requiring that rough diamond exports be accompanied by a government-issued certificate confirming the diamonds did not finance rebel movements. The KP is a minimum standard for conflict-free sourcing; it does not address labour practices, environmental standards, or broader governance. See: Kimberley Process guide.

A type of potassic volcanic rock that serves as the primary host rock for diamond deposits. Kimberlite pipes are the eroded remnants of ancient volcanic conduits through which diamonds were carried from the mantle to the Earth's surface. Named after Kimberley, South Africa, where the first such pipe was commercially mined. See: Kimberlite pipes.

A traditional Indian jewellery technique in which high-purity gold (typically 24kt) is worked into foil around gemstones in a bezel-like setting without soldering. Kundan work is associated with North Indian Mughal jewellery traditions. Kundan pieces may use polki (uncut diamonds), coloured stones, or glass stones set in the same manner.

A diamond grown in a laboratory rather than mined from the Earth, with the same chemical composition (carbon in diamond cubic crystal structure), physical properties, and optical characteristics as a natural diamond. Produced by either CVD or HPHT methods. Distinguishable from natural diamonds only by spectroscopic analysis. See: What is lab-grown?

A clarity enhancement treatment in which a laser channel is drilled from the diamond's surface to a dark inclusion, followed by acid washing to bleach or remove the inclusion. Laser drilling is permanent (the channel cannot be un-drilled), detectable under magnification, and disclosed on GIA certificates. See: Clarity enhancement.

The ratio of a fancy-shaped diamond's length to its width, expressed as a decimal. For an oval diamond, an L/W ratio of 1.30 to 1.50 is considered ideal. For a pear, 1.45 to 1.75. For a marquise, 1.75 to 2.25. Ratios outside these ranges produce stones that appear too round or too elongated. L/W ratio does not appear on GIA certificates and must be calculated from the measurements provided.

A small magnifying lens used by gemologists, jewellers, and diamond graders to examine stones at 10x magnification. The standard for gemological examination is a 10x triplet loupe (three corrective lens elements). GIA clarity grading is defined at 10x magnification under standard conditions. Essential tool for anyone examining estate jewellery or diamond quality.

An elongated brilliant-cut diamond with pointed ends at both sides (also called a navette cut). The marquise has the largest face-up area per carat of any standard diamond shape, making fingers appear longer and slimmer. Requires a high-quality cut to avoid the bowtie effect and a protective setting that covers the vulnerable pointed ends. See: Marquise guide.

Small diamonds, typically below 0.20 carats, used as accent stones in pavé settings, halos, and eternity bands. Melee is bought and sold in parcels rather than individually and is typically not certified. The lack of individual certification makes melee the category most vulnerable to undisclosed mixing of lab-grown diamonds in natural parcels. See: Detecting synthetics.

A decorative border detail on jewellery settings consisting of tiny metal beads rolled along the metal edge. Milgrain is characteristic of Edwardian and Art Deco jewellery and is applied by milgrain wheel or by hand. Under magnification, hand-applied period milgrain shows slight bead size irregularity; modern machine-produced milgrain is more uniform. See: Art Deco jewellery.

A diamond cut that combines brilliant-style facets on the crown with step-cut facets on the pavilion (or vice versa). The radiant cut is the most common mixed cut: it has step-cut facets in a rectangular outline with brilliant facets producing high fire and brilliance. See: Radiant cut guide.

A scale from 1 to 10 measuring a material's resistance to scratching, developed by Friedrich Mohs in 1812. Diamond is 10, the maximum. Corundum (ruby, sapphire) is 9. The scale is not linear: diamond is approximately 58 times harder than corundum (9 on the scale), not merely 1 unit harder.

A portion of the original rough diamond's skin left on a polished stone, appearing as a slightly rough or orange-peel textured area at the girdle. Naturals indicate that the cutter retained the rough's original surface to maximise carat yield. A natural visible to the unaided eye reduces value more than one visible only under magnification.

A long, thin, rod-like crystal inclusion in a diamond, appearing as a thin white line under magnification. Needles are typically inert and have minimal effect on clarity grades unless they are numerous or large enough to be eye-visible.

The most common impurity in natural diamonds, present as substituted carbon atoms in the crystal lattice. Nitrogen gives most natural diamonds a slight yellowish tint (Type Ia diamonds) and produces specific absorption patterns detectable by FTIR spectroscopy. The aggregation state of nitrogen reflects geological age and thermal history. See: Diamond science.

An antique diamond cut with a circular outline, high crown, small table, and large visible culet, produced approximately 1890 to 1930. The OEC is the bridge between the old mine cut and the modern round brilliant and is associated with Edwardian and early Art Deco jewellery. Its slow, warm light flashes differ characteristically from the continuous scintillation of a modern brilliant. See: Antique diamond cuts.

An antique diamond cut with a cushion-shaped outline, high crown, small table, and large visible culet, produced from the 17th century through approximately 1900. The old mine cut is the most widely collected antique cut. Its proportions were designed for candlelight performance and differ fundamentally from modern brilliants. See: Antique diamond cuts.

A modified brilliant cut with an elliptical outline, 58 facets, and light performance similar to a round brilliant. The oval's elongated form makes fingers appear longer and provides a larger face-up area per carat than a round of equivalent weight. Currently the most popular fancy shape for engagement rings in India. See: Oval diamond guide.

A matched set of jewellery typically including a necklace, earrings, bracelet, and brooch or ring. A demi-parure includes two or three matching pieces. Parures are common in antique jewellery (Victorian, Edwardian, Art Deco) and in traditional Indian bridal jewellery suites. When all pieces of a parure are intact, the complete set commands a premium over individual pieces.

The lower portion of a diamond, below the girdle. The pavilion's facets reflect light back up through the crown in a well-cut stone. Pavilion depth and angle are critical to light performance: too shallow and light escapes through the bottom (the "fish-eye" effect); too deep and light leaks through the sides (the "nail-head" effect).

A setting style in which many small diamonds are set close together in a surface, held by tiny beads or prongs, creating an almost continuous diamond surface. Micro-pavé uses very small diamonds (typically 1.0 to 1.5mm). Pavé settings require regular professional maintenance to check and tighten stones. See: Pavé settings.

A modified brilliant cut combining the round and marquise, with one rounded end and one pointed end. The pear shape is the most elongating of all diamond shapes and makes fingers appear longest. The pointed end is vulnerable to chipping and should be protected by a prong. See: Pear diamond guide.

A very small inclusion in a diamond, appearing as a tiny white or black dot under 10x magnification. Individual pinpoints have minimal clarity impact. Clusters of pinpoints form clouds. Pinpoints are among the most common clarity characteristics in natural diamonds and are typically noted at VS2 and below.

One hundredth of a carat. A 0.50 carat diamond is described as "50 points" or "half a carat." A 0.25 carat diamond is "25 points" or "a quarter carat." Points are used in the trade for stones below 1 carat; carat weight is used above 1 carat.

Uncut or minimally cut natural diamonds used in traditional Indian jewellery, particularly jadau and kundan work. Polki diamonds retain the natural crystal form with polished surfaces rather than full faceting. They have a matte or waxy appearance distinct from faceted diamonds and are associated with Mughal and Rajasthani jewellery traditions.

A square brilliant-cut diamond with pointed corners, developed in the 1970s. The princess cut is the second most popular shape after the round brilliant. Its pointed corners are vulnerable to chipping and require corner-protecting prongs. Available in true square (1.00 to 1.05 L/W ratio) and slightly rectangular versions. See: Princess cut guide.

A ring setting in which the diamond is held by metal "prongs" (also called claws or tines) that grip the stone at the girdle. The most common prong counts are four and six; six prongs offer more security. Prong settings allow maximum light entry to the stone but are more vulnerable to snagging and bending than bezel or channel settings. Prongs require periodic inspection and tipping. See: Solitaire settings.

Any of the characteristics assessed in diamond grading: the 4Cs (cut, colour, clarity, carat) plus any treatments, fluorescence, and proportions noted on the certificate. Quality factors collectively determine a diamond's market value within its size category.

A rectangular or square mixed-cut diamond combining a step-cut outline with brilliant-style facets, producing both the architectural look of a step cut and the sparkle of a brilliant. Created by Henry Grossbard in 1977. The most forgiving fancy cut for inclusions because the brilliant facet pattern obscures them better than step cuts. See: Radiant cut guide.

A weekly wholesale price list for polished diamonds published by Rapaport Group, widely used as a benchmark in the diamond trade. Prices are expressed as price per carat for specific size and quality categories of round brilliants. Actual trade prices are expressed as discounts or premiums to Rapaport (e.g., "Rap minus 40%" for a stone selling at 40 percent below the list price). See: Rapaport explained.

A measure of how much a material slows and bends light as it passes through it. Diamond's refractive index is 2.42, among the highest of any natural transparent material. The high RI is responsible for diamond's exceptional brilliance: light bends sharply as it enters and exits the stone, producing the total internal reflection that returns light to the viewer's eye.

A surface treatment applied to white gold jewellery to maintain its bright white appearance. Rhodium is a platinum group metal with a very white, highly reflective surface. White gold naturally develops a slightly yellow cast as the rhodium wears away; replating (which takes 30 to 60 minutes at a jeweller) restores the white surface. Platinum does not require rhodium plating.

An antique diamond cut with a flat base, domed top, and triangular facets converging at a single point, with no pavilion. Produced from the 1500s onward. The rose cut has experienced major collector resurgence since approximately 2010 for its flat profile, organic character, and distinctive surface-reflection light performance. See: Antique diamond cuts.

The most popular and most studied diamond cut. The modern round brilliant has 58 facets in a specific arrangement that maximises brilliance, fire, and scintillation. GIA grades round brilliant cut as Excellent, Very Good, Good, Fair, or Poor based on proportions, symmetry, and polish. GIA Excellent is the standard for fine engagement rings. See: Round brilliant guide.

A diamond with numerous black and white inclusions, giving it a speckled appearance. Salt and pepper diamonds do not meet standard clarity grades but have become popular as an alternative engagement ring choice for buyers who appreciate their organic, distinctive appearance. They are typically set in minimalist or nature-inspired settings that complement their character.

The sparkle the flashes of white and coloured light visible when a diamond or its light source moves. Scintillation is the most immediately appealing visual property of a well-cut diamond and is what most buyers refer to when they say a diamond "sparkles." It is distinct from brilliance (white light return) and fire (coloured light dispersion), though all three are related.

A ring with a flat or lightly domed oval or rectangular face, originally used to press a seal into wax. The tradition is ancient and cross-cultural. Contemporary diamond signet rings for men typically feature a single stone set in the centre of the face in a bezel or flush setting. See: Men's diamond rings.

Approved buyers who purchase rough diamonds directly from De Beers at periodic "Sights" (sales events). Sightholders are the top tier of the De Beers supply chain and include major cutting factories in Surat, Antwerp, and elsewhere. Being a Sightholder requires meeting De Beers' compliance, financial, and operational standards. See: Diamond trade structure.

A construction technique for 19th century jewellery in which the visible setting metal is silver (which shows diamonds to better effect than yellow gold) while the reverse and shank are yellow gold. Silver-topped gold is an identifying characteristic of late Victorian jewellery, produced before platinum became available for fine jewellery settings. See: Victorian jewellery.

A ring setting with a single diamond as the sole stone, held by prongs over a simple band. The solitaire is the most classic and timeless engagement ring configuration, focusing all attention on the diamond. It is the easiest setting to resize and the most easily upgraded. See: Solitaire settings.

The analysis of how matter interacts with light across different wavelengths. For diamonds, the two primary spectroscopic tools are FTIR (infrared absorption for type classification) and photoluminescence (PL) spectroscopy (laser-excited emission for defect identification). GIA uses both tools for all diamonds it grades. See: Diamond science.

A diamond cut style with rectangular or square facets arranged in parallel rows (steps) on both the crown and pavilion. Step cuts include the emerald cut, Asscher cut, baguette, and carré. Step cuts have less brilliance than brilliant cuts but more transparency, revealing the stone's interior and requiring higher clarity grades for best appearance.

The Indian legal concept designating property belonging exclusively to a woman: typically jewellery given at and before marriage, personal gifts, and inheritance. Streedhan is legally protected as the woman's separate property under Indian personal law and cannot be claimed by a husband or his family without the woman's consent. See: Diamonds in Indian life.

A city in Gujarat, India, that processes approximately 90 percent of the world's polished diamonds by volume. Surat's diamond cutting and polishing industry processes both natural and lab-grown diamonds and employs an estimated 400,000 to 500,000 workers. The city is the global centre of small and medium diamond cutting and polishing. See: The Surat story.

One of three components of GIA's cut grade for round brilliants (along with proportions and polish). Symmetry assesses how precisely the facets of a diamond are aligned and shaped: are facets the same size on opposite sides? Are the table and culet centred? Poor symmetry redirects light in unintended directions, reducing light performance. GIA grades symmetry as Excellent, Very Good, Good, Fair, or Poor.

The large, flat facet at the top of a diamond's crown. Table percentage (table width as a percentage of girdle diameter) significantly affects a diamond's light performance. For round brilliants, the ideal table percentage is approximately 54 to 58 percent. A table that is too large reduces fire; a table that is too small reduces brilliance.

A ring setting in which the diamond appears to float in space between two metal arms, held in place by the spring tension of the metal rather than prongs or bezels. The stone is held in channels cut into the metal ends. Tension settings are visually dramatic but require the stone to remain in its exact position for life; the stone cannot be replaced without a new setting. See: Tension settings.

A bracelet of individually prong-set diamonds in a continuous line, secured by a box clasp with a safety mechanism. The name derives from a 1987 US Open incident when tennis player Chris Evert's diamond line bracelet broke on court. Men's tennis bracelets use heavier gauge settings and a longer circumference than women's versions.

A ring setting with a central diamond flanked by two side stones, traditionally representing the past, present, and future of a relationship. The side stones may match the centre stone in shape (three rounds) or contrast with it (a cushion flanked by two tapered baguettes). Side stone quality should be chosen to complement the centre stone. See: Three-stone settings.

The optical phenomenon by which light striking the inside of a diamond's pavilion facets at an angle greater than the critical angle is completely reflected back upward rather than escaping through the bottom. Total internal reflection is the mechanism by which a well-cut diamond returns light to the viewer's eye; poor cut proportions prevent TIR and allow light to leak out of the bottom or sides.

A diamond cut from approximately 1919 to 1940 that represents the transition from old European cut proportions toward modern round brilliant proportions. Transition cuts have a round outline but higher crowns, smaller tables, and different facet arrangements than a standard modern brilliant. Often classified as either late OEC or early modern, transition cuts occupy an interesting position in the antique market.

The classification of diamonds by nitrogen and boron content, as determined by spectroscopic analysis. Type Ia (most natural diamonds, aggregated nitrogen), Type IIa (nitrogen-free, the purest), Type IIb (boron-containing, blue colour), Type Ib (isolated nitrogen, rare in nature, common in HPHT synthetic). GIA determines and may note diamond type on certificates. See: Diamond science.

A cleaning method using high-frequency sound waves in a liquid solution to remove dirt from jewellery. Effective for most diamond settings but problematic for fracture-filled diamonds (the cavitation can damage or expel the filler), diamonds with significant feather inclusions (repeated ultrasonic cleaning may open feathers), and some antique settings. Always confirm enhancement status before ultrasonically cleaning a piece.

The second-highest GIA cut grade for round brilliants (below Excellent). VG cut diamonds reflect most light that enters and offer performance similar to Excellent at a modest price saving. For buyers who cannot find an Excellent cut stone in their target size and quality combination, Very Good is an acceptable alternative.

Very Very Slightly Included 1 and 2: the third and fourth clarity grades on the GIA scale (below FL and IF). VVS inclusions are extremely difficult to see under 10x magnification even for trained graders, and completely invisible to the unaided eye. The visual difference between VVS and VS1 is imperceptible without magnification; the price premium for VVS over VS is commercially significant but aesthetically irrelevant in a set ring.

Very Slightly Included 1 and 2: the fifth and sixth clarity grades on the GIA scale. VS inclusions are visible under 10x magnification but not to the unaided eye. VS2 represents the practical sweet spot for most buyers: eye-clean appearance at a meaningful saving over VVS grades. VS1 offers more confidence in eye-clean appearance with most VS2 stones also being eye-clean.

The industry body that developed the System of Warranties, the voluntary chain-of-custody declaration system for conflict-free diamonds. The WDC warranty statement appears on invoices at all levels of the diamond supply chain. Participation in the WDC System of Warranties is a standard expectation for legitimate diamond traders. See: WDC System of Warranties.

An alloy of gold with white metals (nickel, palladium, or zinc) that produces a pale yellow-white metal. White gold jewellery is typically rhodium-plated to achieve a bright white surface. 18kt white gold (750 parts gold) is the standard for fine diamond jewellery. Requires rhodium replating every one to two years for daily-worn rings. See: Metals guide.

An analytical technique that identifies elemental composition by measuring the secondary X-rays emitted when a material is exposed to X-rays. Used in gemological laboratories to detect metal alloy composition, surface treatments, and in some cases to identify specific elements in gemstone inclusions or in clarity enhancement fillers.

A diamond sorting technology that measures how X-rays are transmitted through individual stones, detecting diamonds by their specific absorption characteristics. XRT sorters are used at diamond mines to separate diamond from waste rock and to identify diamonds in bulk ore. A key technology in modern large-scale diamond recovery operations. See: Mining technology.

The traditional form of gold jewellery, an alloy of gold with silver and copper. 18kt yellow gold (750) is the standard for fine diamond jewellery in India and globally. Yellow gold does not require surface treatment, develops an appealing patina with age, and has the cultural resonance of India's gold jewellery tradition. The warmth of yellow gold can visually enhance diamonds in the G-J colour range. See: Metals guide.

The weight of polished diamond recovered from a rough stone, expressed as a percentage of the rough weight. Diamond yield typically ranges from 30 to 55 percent depending on rough quality, shape, and cutter choices. A higher yield does not automatically mean a better polished stone; cutting for maximum yield may sacrifice proportions. The decision between maximising yield and maximising light performance is central to the diamond cutting process.

Uneven distribution of colour in a diamond, appearing as areas of stronger or weaker colour in different parts of the stone. Colour zoning is a natural growth characteristic and is noted on GIA certificates when present. In face-up position in a well-chosen setting, some zoning may be invisible; in face-down inspection, it may be more apparent. A stone with concentration of colour near the culet may appear more evenly coloured face-up than its GIA colour grade suggests.