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diamond-gemology-encyclopedia

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A Diamond Is Forever	History and myths	"A Diamond Is Forever" is the De Beers advertising slogan written by copywriter Frances Gerety in 1947, later named by Advertising Age the top advertising slogan of the twentieth century.	The line was written by Frances Gerety, a copywriter at the Philadelphia agency N.W. Ayer, in 1947, for the De Beers account. In 1999, Advertising Age named it the number one advertising slogan of the twentieth century. Its staying power comes from a simple pairing: a diamond is the hardest natural material, a 10 on th...	[ { "claim": "The slogan \"A Diamond Is Forever\" was written by copywriter Frances Gerety at the N.W. Ayer agency for De Beers in 1947.", "source": "De Beers Group, Our History and Heritage (company timeline)", "date": "1947 timeline entry; page accessed 2026-09-08", "url": "https://www.debeersgroup....	[ "The months-of-salary rule", "The 4Cs", "Round brilliant cut", "Engagement ring history", "Lab Grown Diamonds" ]
Annual Prong Check	Care and buying	An annual prong check is a yearly appointment where a jeweler inspects the small metal claws holding your diamond and re-tightens or rebuilds any that have worn down. It is the single best habit for not losing a stone.	Prongs are the small metal tips that curl over the edge of a diamond to hold it in place. They take the brunt of daily life: every time a ring bumps a doorknob, a countertop, or a car door, the prongs absorb it. Over months and years that contact wears the metal thin, and a thin prong can bend, snag, or break. When a p...	[ { "claim": "Prongs wear and loosen over time and can let a stone fall out; jewelers advise having prongs checked regularly (every six months, or at least yearly), and tightening prongs is routine bench work.", "source": "GIA 4Cs blog, How to Protect Your Diamond Engagement Ring", "date": "2017-09-26", ...	[ "Prong Setting", "Cleaning a Diamond Ring at Home", "Insuring an Engagement Ring", "Ultrasonic Cleaners", "Setting Styles" ]
asscher cut	Cuts and shapes	An Asscher cut is a square step cut with cut corners, essentially a square emerald cut with deeper, more pronounced steps that draw the eye toward the center in an X or windmill pattern. It reads as a nearly octagonal square with concentric squares of light.	The Asscher belongs to the step-cut family, the same family as the emerald cut. Its outline is square rather than rectangular, with the four corners cut off so that it appears almost octagonal. The step facets are usually cut steeper and deeper than an emerald cut's, and the pavilion draws down to a small center, produ...	[ { "claim": "The Asscher cut was developed in 1902 by Joseph Asscher; it is nearly octagonal in outline and carries 58 large, wide-set step facets in three rows on the crown and three on the pavilion.", "source": "GIA 4Cs blog, The Asscher Cut: A Cut of Royalty and Reinvention", "date": "accessed 2026-09...	[ "emerald cut", "step cut", "princess cut", "cushion cut", "table", "four Cs" ]
bezel setting	Settings and metals	A bezel setting surrounds the diamond with a continuous metal rim that grips the stone around its girdle. It is the most protective common setting, covering and cushioning the stone's edges.	In a bezel setting, a thin wall of metal is shaped to follow the outline of the stone and then pressed over the edge so it holds the diamond the way a frame holds a picture. A full bezel encircles the whole stone. Because the rim covers the girdle, the thin outer edge where chips usually start, and sits flush or nearly...	[ { "claim": "A bezel setting holds the stone with a thin continuous rim of metal around its edge; it protects the perimeter against chips and wear, has no exposed prongs to snag, suits people who work with their hands, and admits slightly less light than prongs. A full bezel encircles the stone; a partial (half)...	[ "prong setting", "half bezel", "girdle", "solitaire", "platinum", "cathedral setting" ]
bow-tie effect	Diamond anatomy	The bow-tie effect is a dark, bow-tie-shaped shadow across the center of many elongated diamond shapes. It is normal light behavior in these outlines, not a flaw.	The bow-tie effect is a shadow shaped like a bow tie, or two dark triangles meeting point to point, seen across the middle of many elongated diamonds when you look at them face-up. It shows up in ovals, pears, marquises, and elongated hexagonal cuts, among others. It's a product of geometry, not a defect. In a stretch...	[ { "claim": "The bow-tie is a dark area of contrast across the width of oval, pear and marquise diamonds; it is produced by the elongation of the outline and is enhanced by pavilion facet arrangements, so it is a product of geometry rather than a defect.", "source": "GIA, Gems & Gemology, Fall 2024, Vol. 60 ...	[ "length-to-width ratio", "pavilion", "oval cut", "marquise cut", "Dutch Marquise" ]
Brilliance	Light and optics	Brilliance is the brightness a diamond returns to the eye: the white light reflected from its surface and, mostly, from inside the stone after it bounces off the pavilion facets. In GIA's cut model this white light return is called brightness, one of the three components of face-up appearance.	Brilliance has two parts. External brilliance is white light that reflects straight off the surface of the crown facets and the table. Internal brilliance is light that enters the stone, bounces off the pavilion facets by total internal reflection, and returns up through the crown and table to your eye. Most of the bri...	[ { "claim": "GIA released its round brilliant cut grading system in January 2006; it assesses face-up appearance through brightness (white light return), fire, and scintillation, and assigns a cut grade from Excellent to Poor.", "source": "GIA (Gemological Institute of America), Diamond Cut grading system, g...	[ "fire (dispersion)", "scintillation", "total internal reflection", "light performance", "cut grade" ]
Carat	The 4Cs and grading	A carat is the standard unit of weight for a diamond, equal to exactly 200 milligrams (0.2 grams). It measures weight, not physical size or diameter, and each carat divides into 100 points.	Carat is usually the first C a buyer asks about, because it's the one figure that reads like a headline number. It rewards precise understanding. One metric carat equals exactly 200 milligrams, and jewelers split each carat into 100 points, so a 25-point diamond weighs a quarter of a carat. Don't confuse carat with kar...	[ { "claim": "The Cullinan is the largest gem-quality rough diamond ever found, at 3,106 carats, recovered in 1905.", "source": "Gemological Institute of America (GIA)", "date": "1905" }, { "claim": "One metric carat equals exactly 200 milligrams and each carat is divided into 100 points.", "s...	[ "the 4Cs", "cut grade", "color grade", "clarity grade", "round brilliant cut" ]
cathedral setting	Settings and metals	A cathedral setting supports the center diamond with two arches of metal that sweep up from the band to the stone, like the arches of a cathedral. The arches add height, security, and a graceful profile.	In a cathedral setting, the shoulders of the band do not run straight into the center stone. Instead they rise in curved arches that meet the setting on each side, cradling the stone from below and lifting it up. The name comes from the resemblance to the arched, vaulted architecture of a cathedral. Those arches are st...	[ { "claim": "A cathedral setting uses arches of metal that rise from the shank to support and lift the center setting; the raised profile is more likely to catch on clothing, while the arches add stability and leave open space beneath the stone for detail work.", "source": "GIA 4Cs, Complete Guide to Engagem...	[ "solitaire", "prong setting", "halo", "pave", "bezel setting", "V-tip prong" ]
Certification labs	The 4Cs and grading	Certification labs, more precisely gemological grading laboratories, are independent organizations that examine and grade diamonds to published standards. For Lab Grown Diamonds today the main names are GIA, IGI, and GCAL, and the landscape shifted noticeably in 2025 and 2026.	GIA, the Gemological Institute of America, is the nonprofit founded by Robert M. Shipley in 1931 that built the 4Cs framework the whole trade uses. It grades both mined and laboratory-grown stones. On October 1, 2025, GIA moved its Lab Grown Diamond reports to a Premium and Standard tier structure, a change from the le...	[ { "claim": "GIA moved its Lab Grown Diamond reports to Premium and Standard tiers on October 1, 2025, dropping the natural-diamond 4C nomenclature for them.", "source": "GIA press release, GIA Launches Updated Laboratory-Grown Diamond Services", "date": "2025-08-26", "url": "https://www.gia.edu/gia-...	[ "the 4Cs", "grading report", "laser inscription", "cut grade", "Lab Grown Diamond" ]
Clarity grade	The 4Cs and grading	A clarity grade rates how free a diamond is of internal inclusions and surface blemishes when examined under 10x magnification, on a scale from Flawless down to Included. It describes tiny features inside and on the stone, most of which the naked eye can't see.	The GIA scale, from best to most included, runs Flawless (FL), Internally Flawless (IF), Very Very Slightly Included (VVS1 and VVS2), Very Slightly Included (VS1 and VS2), Slightly Included (SI1 and SI2), and Included (I1, I2, I3). The reference condition is always 10x magnification: a Flawless diamond shows no inclusi...	[ { "claim": "IGI still issues full 4C grading reports, including a clarity grade, for laboratory-grown diamonds.", "source": "IGI press release, IGI Reaffirms Commitment to 4Cs Grading for all Diamonds (Mumbai)", "date": "2025-07-17", "url": "https://www.igi.org/igi-reaffirms-commitment-to-4cs-gradin...	[ "the 4Cs", "eye-clean", "inclusion", "laser inscription", "grading report" ]
Cleaning a Diamond Ring at Home	Care and buying	You can clean a diamond ring at home with warm water, a little mild dish soap, and a soft brush. Soak it a few minutes, gently brush around and behind the stone, rinse, and pat dry.	A diamond ring picks up a film of hand lotion, soap scum, cooking oils, and skin oil over ordinary wear. Diamond is oleophilic, meaning grease clings to it, so even a spotless-looking stone dulls a little as that film builds. The good news is that removing it is simple and safe to do yourself. Fill a small bowl with w...	[ { "claim": "Diamond ranks 10, the maximum, on the Mohs scale of mineral hardness.", "source": "Mohs scale of mineral hardness (Friedrich Mohs)", "date": "1812" }, { "claim": "Clean a diamond ring with dish soap and warm water and a soft toothbrush; avoid bleach, chlorine and ammonia, which can d...	[ "Ultrasonic Cleaners", "Annual Prong Check", "Mohs Scale", "Prong Setting", "Diamond Durability" ]
Color grade	The 4Cs and grading	A color grade rates how close a diamond is to having no color at all, on GIA's D-to-Z scale where D is completely colorless and Z shows a light yellow or brown tint. In this range less color is rarer, and the grade describes the faint body color you're trying not to see.	The standard scale runs from D at the colorless top to Z at the light end, divided into named bands: D to F is colorless, G to J is near colorless, K to M is faint, N to R is very light, and S to Z is light. Graders judge color by comparing a stone, table-down, against a set of masterstones under controlled lighting, s...	[ { "claim": "GIA's D-to-Z color scale was introduced as part of Richard Liddicoat's International Diamond Grading System in 1953, and the scale starts at D to avoid confusion with earlier trade systems that had used A, B and C.", "source": "Gemological Institute of America (GIA)", "date": "1953" }, {...	[ "the 4Cs", "clarity grade", "fluorescence", "fancy color diamond", "grading report" ]
crown	Diamond anatomy	The crown is the upper part of a diamond, the whole section above the girdle. It includes the flat table and the angled facets that ring it.	The crown is everything above the girdle. It holds the flat table at the top and the ring of angled facets around it, which on a round brilliant are the star facets, the bezel (kite) facets, and the upper girdle facets. The crown has two jobs. It lets light into the stone, and as light leaves, its angled facets bend a...	[ { "claim": "The crown is the upper portion of the diamond, from the top edge of the girdle to the table; crown angle is the angle where the bezel facets meet the girdle plane; crown height is expressed as a percentage of average girdle diameter; appearance arises from the combined contribution of all proportion...	[ "table", "girdle", "pavilion", "crown angle", "facet" ]
Cubic zirconia	Materials and simulants	Cubic zirconia (CZ) is a lab-made crystalline form of zirconium dioxide (ZrO2), stabilized into a cubic structure and cut as an inexpensive, colorless diamond simulant. It is a different material from diamond, softer and denser, and is not a type of diamond.	Zirconium dioxide does not naturally hold a cubic crystal form at room temperature, so cubic zirconia has to be coaxed into one. Makers add a stabilizer such as yttrium oxide or calcium oxide and melt the mixture at extreme temperature (zirconia melts near 2,750 degrees Celsius) using a skull-melting method, in which t...	[ { "claim": "The skull-melting process for producing cubic zirconia crystals was developed by Soviet researchers at the Lebedev Physical Institute in Moscow, with the method published in 1973.", "source": "Lebedev Physical Institute (V. V. Osiko group); cubic zirconia history, per encyclopedic and gemologica...	[ "Diamond (the material)", "Moissanite", "White sapphire", "Simulant vs synthetic", "Mohs hardness" ]
culet	Diamond anatomy	The culet is the point or small facet at the very bottom of a diamond, where the pavilion facets meet. On many modern stones it is a clean point, graded as none.	The culet is the point or tiny facet at the very bottom of a diamond, where the pavilion facets come together. On many modern stones there's no facet there at all, just a clean point, which a grading report lists as a culet of none or pointed. Historically, cutters polished a small facet across the bottom tip to guard...	[ { "claim": "The culet is the small facet at the bottom of a diamond intended to prevent chipping of the point; culet size is graded none, very small, small, medium, slightly large, large, very large, extremely large; no culet is also called pointed.", "source": "GIA 4Cs, \"Diamond Anatomy, Explained\"", ...	[ "pavilion", "girdle", "facet", "old European cut", "crown" ]
cushion cut	Cuts and shapes	A cushion cut is a square-to-rectangular diamond with rounded corners and gently curved sides, faceted in the brilliant style, so that it resembles a pillow. It offers soft, rounded sparkle and a slightly antique character.	The cushion is a modified brilliant whose outline is a square or rectangle with the corners and sides rounded, giving it the pillow shape that names it. Brilliant-style faceting fills the interior, and cushions come in two broad faceting styles: a chunky pattern with larger, bolder facets, and a crushed-ice pattern wit...	[ { "claim": "A cushion has a square or rectangular outline with rounded corners and comes in two faceting styles: brilliant (larger facets, softer sparkle) and modified brilliant (extra facets, crushed-ice effect).", "source": "GIA 4Cs blog, Guide to Diamond Engagement Ring Shapes", "date": "2025-11-21",...	[ "elongated cushion", "old mine cut", "brilliant cut", "princess cut", "crushed-ice faceting", "length-to-width ratio" ]
Cut grade	The 4Cs and grading	A cut grade rates how well a diamond's proportions, symmetry, and polish return light to the eye, which is what makes a diamond look bright and lively. GIA grades cut for standard round brilliant diamonds on a five-step scale from Excellent to Poor.	Of the four C's, cut is the one most under human control and the one that most drives how a diamond actually looks. Color and clarity describe the raw crystal; cut describes the craft applied to it. A cutter chooses angles and proportions that either send light back up through the top of the stone or leak it out the bo...	[ { "claim": "Marcel Tolkowsky published Diamond Design in 1919, a mathematical study of light reflection and refraction in a diamond that proposed proportions for the round brilliant.", "source": "Marcel Tolkowsky, Diamond Design: A Study of the Reflection and Refraction of Light in a Diamond (London: E. & F...	[ "the 4Cs", "round brilliant cut", "Dutch Marquise", "carat", "grading report" ]
CVD Growth	Lab Grown Diamonds	CVD (Chemical Vapor Deposition) is a method of growing diamond by breaking a carbon-rich gas down inside a vacuum chamber so that carbon atoms settle onto a thin diamond seed and build a crystal up layer by layer.	CVD grows a diamond from gas. The process starts with a thin, flat slice of diamond called a seed, placed inside a sealed vacuum chamber. A carbon-rich gas, usually methane, is fed in along with hydrogen. Energy, typically microwaves, heats the gas into a glowing plasma and breaks the molecules apart, freeing individua...	[ { "claim": "CVD grows diamond inside a vacuum chamber from a hydrogen and methane gas mix broken down by microwave energy; carbon deposits on flat diamond seed plates; the method runs at lower pressure than HPHT; crystals grow flat and tabular; as-grown brown color is removed by HPHT annealing.", "source": ...	[ "HPHT Growth", "Post-Growth Treatment (HPHT Annealing)", "Lab Grown Diamond", "Inclusions in Lab Grown Diamonds", "Diamond Type IIa" ]
depth percentage	Diamond anatomy	Depth percentage is a diamond's total height (table to culet) divided by its average girdle diameter, expressed as a percentage. It tells you how deep or shallow the stone is cut relative to its width.	Depth percentage is a single number that tells you how tall a diamond is compared with how wide it is. The formula is the total depth, measured from the table on top down to the culet at the bottom, divided by the average girdle diameter, then multiplied by one hundred. It matters because depth controls how light trav...	[ { "claim": "Marcel Tolkowsky published influential round brilliant proportions, covering depth and facet angles, in 1919.", "source": "Marcel Tolkowsky, Diamond Design (1919)", "date": "1919" }, { "claim": "Total depth percentage is the table-to-culet depth expressed as a percentage of the avera...	[ "table percentage", "girdle", "pavilion", "cut", "crown angle" ]
Diamond (the material)	Materials and simulants	Diamond is a crystalline form of pure carbon, with each carbon atom bonded to four others in a rigid cubic (isometric) lattice. That structure makes it the hardest known natural material, a 10 on the Mohs scale, and an exceptional conductor of heat.	Diamond is carbon, the same element found in graphite and charcoal, but arranged very differently. In graphite the carbon atoms sit in loose sheets that slide past one another, which is why it feels slippery and marks paper. In diamond every carbon atom is locked to four neighbors in a three-dimensional tetrahedral fra...	[ { "claim": "The FTC defines a diamond as a mineral consisting essentially of pure carbon crystallized in the isometric system, with hardness 10, specific gravity about 3.52 and refractive index 2.42.", "source": "eCFR, 16 CFR 23.12, Definition and misuse of the word 'diamond' (FTC Jewelry Guides)", "dat...	[ "Lab Grown Diamond", "Mohs hardness", "Thermal conductivity and diamond testers", "Toughness vs hardness", "Moissanite" ]
Do diamonds come from coal?	History and myths	Mostly no. Almost all natural diamonds form deep in Earth's mantle from carbon-rich material, and most are far older than the land plants that coal is made from, so coal is not their source.	Mostly no. The popular image of a lump of coal squeezed into a diamond makes a nice story, but it does not match the geology. Almost all natural diamonds form deep inside the Earth's mantle, roughly 90 to 125 miles (150 to 200 km) below the surface, where extreme pressure and heat let carbon crystallize over very long ...	[ { "claim": "Most natural diamonds form deep in Earth's mantle, roughly 150 kilometers (about 90 miles) or more below the surface, under high pressure and temperature, and are carried upward by kimberlite volcanic eruptions.", "source": "GIA, \"Diamonds from the Deep: How Do Diamonds Form in the Deep Earth?\...	[ "Kimberlite", "Diamond formation", "Lab Grown Diamonds", "HPHT and CVD growth", "Carbon", "Mohs scale" ]
Do Lab Grown Diamonds Cloud or Fade?	Lab Grown Diamonds	No. Lab Grown Diamonds do not cloud, fade, yellow, or degrade over time; a Lab Grown Diamond is crystallized carbon, and its color and clarity are fixed properties of the crystal that don't change with age or wear.	This is one of the most common worries about Lab Grown Diamonds, and the answer is a plain no. A diamond, grown or mined, is carbon locked in an extremely stable crystal structure and rated 10 on the Mohs scale, the hardest of any natural material. Its color and clarity are set by the arrangement of the crystal itself,...	[ { "claim": "A Lab Grown Diamond is a diamond with the same chemical, physical and optical properties as a natural diamond; simulants such as cubic zirconia are different materials, and CZ scratches more easily than diamond and may yellow over time.", "source": "GIA 4Cs, What Are Simulated Diamonds?", "d...	[ "Lab Grown Diamond", "Diamond Simulant", "Cubic Zirconia", "Post-Growth Treatment (HPHT Annealing)", "Lab-Grown vs Mined Diamonds" ]
Dutch Marquise	Cuts and shapes	A Dutch Marquise is an elongated hexagonal cut diamond. It has pointed ends and straight, angular sides, and it is a trade name, not an official gemological shape category; on a laboratory report the same shape is described as a Hexagonal Modified Brilliant.	A Dutch Marquise is an elongated hexagon in outline: two pointed ends joined by straight, angular sides, rather than the curved sides of a true marquise. That straight-sided geometry is what separates it from the classic marquise, or navette, which is a boat shape with two points but sides that curve outward. The Dutch...	[ { "claim": "IGI report LG799689559, issued May 9, 2026, describes the stone as a laboratory grown diamond with shape and cut Hexagonal Modified Brilliant, 1.03 ct, measuring 9.49 x 5.15 x 3.36 mm (length-to-width 1.84), inscription IGI LG799689559.", "source": "IGI (International Gemological Institute), Ver...	[ "hexagon cut", "marquise cut", "navette", "length-to-width ratio", "IGI report" ]
east-west setting	Settings and metals	An east-west setting turns an elongated diamond sideways so its long axis runs across the finger, from side to side, instead of up and down the finger. It is a modern, less common way to set shapes like ovals, marquises, emeralds, and pears.	Most rings set an elongated stone lengthwise, with its long axis running along the finger toward the wrist. An east-west setting rotates that same stone a quarter turn so it lies horizontally, spanning the width of the finger. The stone and the setting are otherwise the same; only the orientation changes. It is a simpl...	[ { "claim": "An east-west setting turns an elongated (here oval) diamond horizontally across the finger instead of vertically.", "source": "GIA 4Cs, \"Oval Cut Diamond Buying Guide\"", "date": "undated page; accessed 2026-09-08", "url": "https://4cs.gia.edu/en-us/blog/oval-cut-diamond-guide/" }, ...	[ "solitaire", "half bezel", "marquise cut", "emerald cut", "Dutch Marquise", "oval cut" ]
elongated cushion	Cuts and shapes	An elongated cushion is a cushion cut with a rectangular rather than square outline, stretched so its length clearly exceeds its width while keeping the soft rounded corners and pillow silhouette. It is a longer, more finger-flattering version of the standard cushion.	An elongated cushion is not a separate faceting family; it is a cushion cut, a modified brilliant with rounded corners and curved sides, drawn out to a longer length-to-width ratio. Where a classic cushion is close to square, an elongated cushion typically runs at a ratio of roughly 1.2 to one or more, giving it a rect...	[ { "claim": "Cushions exist in elongated, rectangular proportions as well as rounded squares.", "source": "GIA 4Cs blog, The Cushion Cut Engagement Ring, A Classic Shape", "date": "2017-05-30", "url": "https://4cs.gia.edu/en-us/blog/diamond-cushion-cut-engagement-ring/" }, { "claim": "An elon...	[ "cushion cut", "oval cut", "radiant cut", "length-to-width ratio", "crushed-ice faceting", "brilliant cut" ]
emerald cut	Cuts and shapes	An emerald cut is a rectangular diamond with cut (beveled) corners and step-cut faceting: long, flat, parallel facets stacked in rows like stairs, viewed through a large open table. It trades sparkle for a clean, glassy look and long flashes of light.	The emerald cut is the classic step cut. Instead of the many small triangular facets of a brilliant, it has a smaller number of long rectangular facets running parallel to the girdle, stacked in steps on the crown and pavilion. The corners are cut off at an angle, turning the rectangle into an elongated octagon, and th...	[ { "claim": "An emerald cut is rectangular with beveled corners and concentric rows of step facets on crown and pavilion; its long facets make inclusions more visible and its lower scintillation makes body color more apparent, so higher clarity and color grades are advisable.", "source": "GIA 4Cs, Emerald Cu...	[ "step cut", "asscher cut", "radiant cut", "table", "four Cs", "baguette" ]
Eye-clean	The 4Cs and grading	Eye-clean describes a diamond with no inclusions or blemishes visible to a person with normal vision at a typical viewing distance. It's a practical trade description, not an official grade on the clarity scale.	Clarity grades are assigned under 10x magnification, but you don't wear a diamond at 10x. Eye-clean bridges that gap by describing what the stone looks like to the unaided eye at normal viewing distance, usually taken to be roughly a foot away, in ordinary light. A diamond can carry inclusions that a grader records und...	[ { "claim": "Eye-clean is an industry term for a diamond whose inclusions cannot be seen with the naked eye; GIA does not use the term; clarity grades are determined at 10x magnification.", "source": "GIA 4Cs, Seven Things to Know When Looking at Diamond Clarity", "date": "2018-04-17", "url": "https:...	[ "clarity grade", "the 4Cs", "inclusion", "emerald cut", "grading report" ]
facet	Diamond anatomy	A facet is a single flat, polished surface on a diamond. The number, shape, angle, and alignment of all the facets together make up the cut.	A facet is one flat, polished plane on the surface of a diamond. Each one behaves either as a window, letting light pass in or out, or as a mirror, bouncing light around inside the stone. Taken together, the number of facets, their shapes, their angles, and how precisely they line up make up what we call the cut, and t...	[ { "claim": "Marcel Tolkowsky published an influential set of proportions for the round brilliant in Diamond Design, 1919.", "source": "Internet Archive, Diamond design, by Marcel Tolkowsky (Library of Congress scan)", "date": "1919 (publication); record accessed 2026-09-08", "url": "https://archive....	[ "table", "crown", "pavilion", "culet", "cut" ]
Finding Your Ring Size	Care and buying	Finding your ring size means measuring the finger the ring will sit on to get a size number. The most reliable way is to have a jeweler size you with a set of metal ring gauges, but you can also measure at home with a ring sizer or by measuring a ring that already fits.	Ring size is a standardized measurement of the inside of a band. In the United States it is expressed as a number, with half sizes, that corresponds to a specific inside diameter and circumference. Getting it right matters, because a ring that is too loose can spin or slip off, and one that is too tight is uncomfortabl...	[ { "claim": "The most accurate method is to have a jeweler determine the size; plastic ring sizers give a fairly accurate measurement; string and paper are the least reliable.", "source": "GIA 4Cs blog, How to Determine Ring Size: Tips and Ring Size Chart", "date": "2018-01-18", "url": "https://4cs.g...	[ "Made-to-Order vs. Ready-to-Ship", "Ring Resizing", "Eternity Band", "Band Width", "Setting Styles" ]
Fire (dispersion)	Light and optics	Fire is the flashes of spectral color a diamond throws when white light splits into its component colors inside the stone. Its physical cause is dispersion: a diamond's refractive index is slightly different for each wavelength, so each color bends by a different amount.	White light is a mix of all colors. When it enters a diamond it slows and bends, and because the diamond bends violet light a little more than red light, the colors fan out and leave the stone along slightly different paths. Your eye catches those separated colors as brief red, orange, blue, and violet flashes. That is...	[ { "claim": "GIA's round brilliant cut grading system (released January 2006) assesses face-up appearance through brightness, fire, and scintillation.", "source": "GIA (Gemological Institute of America), Diamond Cut grading system, gia.edu / 4cs.gia.edu", "date": "2006-01" }, { "claim": "Under th...	[ "brilliance", "scintillation", "refractive index", "cut grade", "moissanite" ]
Fluorescence	The 4Cs and grading	Fluorescence is the visible glow, most often blue, that some diamonds give off under ultraviolet light such as sunlight or a black light. Labs rate its strength from None to Very Strong, and for most diamonds it has little or no effect on how the stone looks in ordinary light.	Roughly speaking, fluorescence happens because certain trace elements and structural features in a diamond absorb ultraviolet energy and re-emit it as visible light. The common color is blue, though other colors occur. GIA reports fluorescence on a scale of None, Faint, Medium, Strong, and Very Strong, describing the r...	[ { "claim": "A GIA study published in Gems & Gemology (Winter 1997) found that, for the average observer, blue fluorescence had no systematic effect on diamond appearance, and strongly blue fluorescent diamonds were perceived slightly better in the face-up position.", "source": "GIA, Gems & Gemology (Moses e...	[ "color grade", "the 4Cs", "grading report", "certification labs", "clarity grade" ]
FTC Definition of Diamond (2018)	Lab Grown Diamonds	In 2018 the U.S. Federal Trade Commission revised its Jewelry Guides and removed the word "natural" from the definition of a diamond, formally recognizing that a diamond grown in a laboratory is still a diamond.	The Federal Trade Commission's Jewelry Guides are the rules that govern how diamonds and jewelry can be described and marketed in the United States. For decades the guides defined a diamond, in effect, as a natural mineral made of carbon crystallized in the isometric system. The word "natural" carried an important impl...	[ { "claim": "The FTC revised its Jewelry Guides and removed the word 'natural' from the definition of a diamond.", "source": "FTC Jewelry Guides (revised)", "date": "2018" }, { "claim": "The FTC advised sellers to disclose lab-grown origin and accepted qualifiers such as 'laboratory-grown', 'labo...	[ "Lab Grown Diamond", "Lab-Grown vs Mined Diamonds", "Grading Report", "Diamond Simulant", "GIA vs IGI Grading" ]
girdle	Diamond anatomy	The girdle is the narrow band around the widest part of a diamond, where the crown meets the pavilion. It forms the stone's outline and is where a setting grips it.	The girdle is the dividing line of a diamond. Everything above it is the crown; everything below is the pavilion. Its outline is the shape you name the stone by, round, oval, cushion, and so on, and it is the practical place a jeweler grips the stone, whether with prongs or a surrounding bezel. Girdle thickness is gra...	[ { "claim": "The girdle is the narrow band between crown and pavilion that serves as the setting edge; thick girdles add hidden weight, extremely thin (knife-edge) girdles chip more easily, and medium to slightly thick is preferred.", "source": "GIA 4Cs, \"Diamond Anatomy, Explained\"", "date": "undated ...	[ "crown", "pavilion", "culet", "depth percentage", "facet" ]
Grading report	The 4Cs and grading	A grading report is a document from an independent gemological laboratory that describes a diamond's measured characteristics, including the 4Cs, on a standard form. It's a scientific description of the stone, not a statement of monetary value or an appraisal.	A typical report lists the shape and cutting style, the measurements in millimeters, the carat weight, the color and clarity grades, and, for round brilliants, a cut grade, along with polish, symmetry, fluorescence, and any laser inscription. Many reports include a plotting diagram that maps the stone's clarity charact...	[ { "claim": "IGI issues full 4C grading reports for Lab Grown Diamonds.", "source": "IGI press release, IGI Reaffirms Commitment to 4Cs Grading for all Diamonds", "date": "2025-07-17", "url": "https://www.igi.org/igi-reaffirms-commitment-to-4cs-grading-for-all-diamonds/" }, { "claim": "GIA mo...	[ "the 4Cs", "certification labs", "laser inscription", "clarity grade", "appraisal" ]
half bezel	Settings and metals	A half bezel, also called a semi-bezel or open bezel, wraps metal around only two sides of the diamond, usually the left and right, leaving the other two sides open. It shields the stone's long sides while letting in more light than a full bezel.	A half bezel is the middle ground between a full bezel and prongs. Two curved walls of metal cup the sides of the stone and hold it firmly, while the top and bottom, or the two ends of an elongated stone, stay open. That open space lets light enter from more directions, so a half-bezeled diamond usually looks brighter ...	[ { "claim": "A bezel is a rim of metal around the stone's edge; a full bezel encircles it completely, a partial bezel leaves sections exposed while still adding security; bezels resist chips and snagging but admit slightly less light than open settings.", "source": "GIA 4Cs, Complete Guide to Engagement Ring...	[ "bezel setting", "prong setting", "V-tip prong", "east-west setting", "girdle", "solitaire" ]
halo	Settings and metals	A halo is a ring of small diamonds set around a larger center stone, framing it with a circle of sparkle that makes the center look bigger and brighter. It is one of the most popular center-stone settings.	A halo surrounds the center diamond with a continuous border of small accent stones, usually pave-set, so the frame reads as one bright ring of light. The main reason people choose a halo is size and sparkle for the money: the border adds visual weight, so a center stone can look noticeably larger than its carat weight...	[ { "claim": "A halo is a center stone surrounded by a ring of smaller accent stones; pave stones are held by tiny beads or prongs.", "source": "GIA 4Cs, Complete Guide to Engagement Ring Settings: Types vs. Styles", "date": "2026-08-14", "url": "https://4cs.gia.edu/en-us/blog/guide-to-ring-settings/"...	[ "hidden halo", "pave", "solitaire", "cathedral setting", "carat", "oval cut" ]
Hearts and arrows	Light and optics	Hearts and arrows is a pattern of eight symmetrical arrows seen face-up and eight hearts seen from the back, visible in a round brilliant cut with very precise optical symmetry and viewed through a special scope. It is a sign of exacting cut symmetry, not a grade of its own.	The pattern comes from the way a round brilliant's facets reflect one another. When the eight pavilion main facets and the eight crown facets are cut to matching angles and spaced evenly, their reflections line up into eight arrowheads when you look straight down through the table, and into eight heart shapes when you ...	[ { "claim": "The hearts and arrows pattern was first observed in Japan during the 1980s, seen in round brilliants of exceptional symmetry through a special viewer, and spread to the United States and Europe over the following decade.", "source": "IGI (International Gemological Institute), education, igi.org"...	[ "scintillation", "light performance", "cut grade", "optical symmetry", "round brilliant" ]
hexagon cut	Cuts and shapes	A hexagon cut is a diamond with a six-sided outline. It is a geometric fancy shape that can be faceted with long parallel facets, in the brilliant style, or as a mix of the two, and can be cut as a regular hexagon or elongated.	A hexagon cut is defined by its outline: six straight sides meeting at six corners. Beyond that, it is an open category. A hexagon can be faceted with long, flat facets stacked parallel to the girdle for a clean, geometric look, or in the brilliant style for more sparkle, or a blend of the two, so two stones both calle...	[ { "claim": "Shape is the outline of the stone and cut (faceting style) is the facet arrangement, so the same outline can carry different facet arrangements.", "source": "GIA 4Cs blog, How Diamonds Shape Up", "date": "2012-06-19", "url": "https://4cs.gia.edu/en-us/blog/how-diamonds-shape-up/" }, ...	[ "Dutch Marquise", "emerald cut", "step cut", "bezel setting", "marquise cut", "brilliant cut" ]
hidden halo	Settings and metals	A hidden halo is a ring of tiny diamonds set on the underside of the center stone's setting, circling the base where it meets the band, so the extra sparkle shows only from the side and profile, not when you look straight down at the ring.	A hidden halo puts a halo where you do not expect one. Instead of framing the center diamond on top, the small stones ring the outside of the basket or collar that holds the center stone, sitting just below it. From directly above, the center diamond looks like a clean solitaire with no frame. Turn the ring to the side...	[ { "claim": "A hidden halo gives the pave sparkle of a traditional halo but hidden, so it adds sparkle without distracting from the center stone and keeps the solitaire look from above.", "source": "JCK (trade press), Brittany Siminitz, The Hidden Halo Engagement Ring Is The New Must-Stock", "date": "202...	[ "halo", "pave", "solitaire", "cathedral setting", "prong setting", "girdle" ]
HPHT Growth	Lab Grown Diamonds	HPHT (High Pressure High Temperature) is a method of growing diamond by dissolving carbon in molten metal and letting it crystallize onto a diamond seed under intense pressure and heat, recreating the kind of conditions under which diamonds form deep in the earth.	HPHT recreates, inside a machine, the pressure and heat that form diamonds underground. A large press squeezes a sealed growth cell to enormous pressure while heating it to a high temperature. Inside sits a carbon source, usually graphite, along with a molten metal that acts as a solvent, commonly iron, nickel, or coba...	[ { "claim": "In HPHT growth a diamond seed sits in a press; graphite dissolves in a molten metal flux of iron, nickel or cobalt at 1300 to 1600 C and very high pressure, migrates to the cooler seed and crystallizes; HPHT crystals typically show cubic faces as well as octahedral ones; nitrogen turns the crystals ...	[ "CVD Growth", "Post-Growth Treatment (HPHT Annealing)", "Lab Grown Diamond", "Inclusions in Lab Grown Diamonds", "Lab-Grown vs Mined Diamonds" ]
Inclusions in Lab Grown Diamonds	Lab Grown Diamonds	Inclusions in a Lab Grown Diamond are the tiny internal features, such as metallic flecks, dark crystals, or faint growth lines, that form while the diamond grows. They're the Lab Grown Diamond counterpart to the inclusions in mined diamonds, and they're what graders read to judge clarity and to confirm how a stone was...	Every diamond has an interior, and most have small features inside called inclusions. Lab Grown Diamonds are no exception. What differs is the kind of inclusion, because it reflects how the stone was grown. HPHT diamonds grow inside a molten metal, so they can carry tiny metallic flux inclusions, specks of the iron, n...	[ { "claim": "IGI grades Lab Grown Diamond clarity at 10X magnification on the same basis as natural stones, and its reports may state the growth method (HPHT or CVD).", "source": "IGI, Laboratory Grown Diamond Report", "date": "2026 (fetched 2026-09-08)", "url": "https://www.igi.org/reports/lab-grown...	[ "HPHT Growth", "CVD Growth", "Lab Grown Diamond", "Diamond Clarity", "The 4Cs", "Grading Report" ]
Insuring an Engagement Ring	Care and buying	Insuring an engagement ring means buying coverage that pays to repair or replace it if it is lost, stolen, or damaged, either as an add-on to a home or renters policy or as a standalone jewelry policy. You will usually need documentation such as the grading report, the receipt, and an appraisal.	An engagement ring is worn constantly and can be lost, stolen, or damaged, and standard home or renters insurance often limits what it will pay for jewelry. Insurance closes that gap. There are two common routes. The first is a rider, also called a floater or scheduled personal property, added to an existing homeowners...	[ { "claim": "Standard homeowners or renters coverage may be insufficient for expensive jewelry; the options are a separate policy or an endorsement (rider); insurers usually require an appraisal; keep photos and the appraisal separately.", "source": "National Association of Insurance Commissioners (NAIC), Co...	[ "Appraisal", "Grading Report", "Verifying a Grading Report", "Annual Prong Check", "Replacement Value" ]
Lab Grown Diamond	Lab Grown Diamonds	A Lab Grown Diamond is a real diamond, pure crystallized carbon with the same crystal structure, hardness, and optical properties as a mined diamond, produced in a laboratory instead of forming underground. The only difference is where the carbon crystallized.	A Lab Grown Diamond is not an imitation or a stand-in. It's the same material as a mined diamond: carbon atoms locked into the same cubic crystal lattice, with the same hardness (10 on the Mohs scale), the same brilliance, and the same fire. Set a grown and a mined diamond of matching grades side by side and no one, in...	[ { "claim": "The FTC removed the word 'natural' from its definition of a diamond, recognizing that a Lab Grown Diamond is a diamond.", "source": "FTC Jewelry Guides (revised)", "date": "2018" }, { "claim": "Laboratory-grown diamonds have essentially the same chemical composition, crystal structur...	[ "CVD Growth", "HPHT Growth", "FTC Definition of Diamond (2018)", "Lab-Grown vs Mined Diamonds", "The 4Cs", "Diamond Simulant" ]
Lab-Grown vs Mined Diamonds	Lab Grown Diamonds	A Lab Grown Diamond and a mined diamond are the same material, with the same hardness, brilliance, and fire; they differ in origin (a laboratory versus the earth) and usually in price, not in what they are.	Start with what's identical, because most of it is. A Lab Grown Diamond and a mined diamond are both pure carbon in the same crystal structure. Both are a 10 on the Mohs scale, the hardest of any natural material. Both bend and return light the same way, so they show the same brilliance and fire. Both are graded by the...	[ { "claim": "Lab-grown and mined diamonds are both recognized as diamonds under the FTC's revised definition.", "source": "FTC Jewelry Guides (revised)", "date": "2018" }, { "claim": "IGI still issues full 4C reports (carat, color, clarity, cut) for Lab Grown Diamonds.", "source": "IGI, How t...	[ "Lab Grown Diamond", "FTC Definition of Diamond (2018)", "Do Lab Grown Diamonds Cloud or Fade?", "The 4Cs", "Diamond Simulant", "Grading Report" ]
Laser inscription	The 4Cs and grading	A laser inscription is text, usually a report number, micro-engraved onto a diamond's girdle with a fine laser and readable under magnification. It lets you match a specific stone to its grading report, and on Lab Grown Diamonds it commonly marks the stone as laboratory-grown.	The girdle is the thin outer edge where the top and bottom of a diamond meet, and it's the standard place for an inscription because it doesn't interfere with how light moves through the stone. The characters are tiny, invisible to the naked eye, and read with a loupe or microscope. Most often the inscription is the gr...	[ { "claim": "GIA laser-inscribes \"Laboratory-Grown\" and the report number on the girdle of Lab Grown Diamonds.", "source": "Gemological Institute of America (GIA)", "date": "2026" }, { "claim": "IGI historically inscribed \"LAB GROWN\" on laboratory-grown diamonds and, from early February 2023,...	[ "grading report", "certification labs", "girdle", "the 4Cs" ]
length-to-width ratio	Diamond anatomy	Length-to-width ratio is a diamond's length divided by its width, both measured across the girdle. It describes how square or elongated the outline is.	Length-to-width ratio comes straight from a diamond's outline measurements: the length in millimeters divided by the width in millimeters, both taken across the girdle. A ratio near 1.00 is square or round; the higher the number, the more elongated the stone. It is used mainly for fancy (non-round) shapes to describe ...	[ { "claim": "The Dutch Marquise is an elongated hexagonal cut (a trade name; an IGI report describes it as 'Hexagonal Modified Brilliant') with no standardized length-to-width ratio; a certified reference stone measures 1.84.", "source": "Stienhardt Dutch Marquise reference; IGI diamond report", "date": ...	[ "bow-tie effect", "Dutch Marquise", "oval cut", "marquise cut", "girdle" ]
Light performance	Light and optics	Light performance is an umbrella term for how well a diamond takes in light and returns it to the eye, combining brightness, fire, scintillation, and the absence of light leakage. It is assessed with ray tracing and with viewers like the ASET and the Idealscope rather than by a single universal grade.	Light performance is the practical question behind cut: of all the light that reaches a diamond, how much comes back to your eye as brightness, colored fire, and sparkle, and how much is wasted by leaking out the bottom. A stone with strong light performance returns most of the light it gathers and spreads it evenly ac...	[ { "claim": "GIA's round brilliant cut grading system (released January 2006) assigns a cut grade from Excellent to Poor based on proportions and on brightness, fire, and scintillation.", "source": "GIA (Gemological Institute of America), Diamond Cut grading system, gia.edu / 4cs.gia.edu", "date": "2006-...	[ "brilliance", "fire (dispersion)", "scintillation", "windowing and light leakage", "cut grade" ]
Made-to-Order vs. Ready-to-Ship	Care and buying	Made-to-order means your ring is built and set after you place the order, so you can choose the stone, setting, metal, and size, but it takes longer. Ready-to-ship means the ring is already finished and in stock, so it arrives fast with less to customize.	These are two ways a finished ring reaches you, and the difference is mostly time versus choice. A made-to-order ring, sometimes called built-to-order, is assembled after you buy it. You typically select the center stone, the setting style, the metal, and the finger size, and the piece is set and finished to those spe...	[ { "claim": "A straightforward custom ring takes at least two weeks; complex designs or stone matching take five to six weeks or longer, so ask the lead time.", "source": "GIA 4Cs blog, Custom Made Engagement Rings Guide", "date": "accessed 2026-09-08", "url": "https://4cs.gia.edu/en-us/blog/guys-gui...	[ "Finding Your Ring Size", "The Eye-Clean Buying Strategy", "Setting Styles", "Ring Resizing", "Grading Report" ]
marquise cut (navette)	Cuts and shapes	A marquise cut, also called a navette, is an elongated, boat-shaped diamond with two pointed ends and gently curved sides, faceted in the brilliant style. It shows one of the largest face-up spreads per carat of any shape.	The marquise is a modified brilliant with an elongated outline that comes to a point at each end. The sides curve outward from the middle, and brilliant-style facets fill the interior, so it sparkles like a round or an oval rather than flashing like a step cut. It is also called a navette, from the French for a small b...	[ { "claim": "Diamond is the maximum, a 10, on the Mohs scale of mineral hardness.", "source": "Mohs scale of mineral hardness", "date": "1812" }, { "claim": "The marquise is an elongated diamond with curved sides and pointed ends, also called a navette (Old French for little ship); it looks large...	[ "navette", "brilliant cut", "pear cut", "bow-tie effect", "prong setting", "Dutch Marquise" ]
Mohs hardness	Materials and simulants	The Mohs scale is a 1-to-10 ordinal ranking of a mineral's resistance to being scratched, where a higher-numbered mineral can scratch any lower-numbered one. Diamond sits at 10, the top of the scale.	The Mohs scale was devised in 1812 by the German mineralogist Friedrich Mohs as a simple field test. Take two minerals, try to scratch one with the other, and whichever leaves a mark is the harder. Mohs fixed ten reference minerals as benchmarks, from talc at 1 (soft enough to mark with a fingernail) up through gypsum,...	[ { "claim": "The Mohs hardness scale (an ordinal 1-to-10 scratch scale running talc 1, gypsum 2, calcite 3, fluorite 4, apatite 5, feldspar 6, quartz 7, topaz 8, corundum 9, diamond 10) was devised by the German mineralogist Friedrich Mohs.", "source": "Friedrich Mohs, Versuch einer Elementar-Methode zur nat...	[ "Toughness vs hardness", "Diamond (the material)", "Moissanite", "White sapphire", "Cubic zirconia" ]
Moissanite	Materials and simulants	Moissanite is silicon carbide (SiC), a hard, brilliant crystalline material used both as a diamond simulant and as a gemstone in its own right. Almost all moissanite in jewelry is lab-created, because the natural mineral is vanishingly rare.	Moissanite is not a type of diamond, and it is not a lower grade of anything. It is a separate material, silicon carbide, with its own chemistry and its own look. The French chemist Henri Moissan found small crystals in fragments of a meteorite from Canyon Diablo in Arizona in 1893, and first mistook them for diamond. ...	[ { "claim": "Henri Moissan found small crystals in fragments of a meteorite from Canyon Diablo, Arizona, and initially believed them to be diamond.", "source": "Historical account of Moissan's meteorite analysis, per mineralogical references (Mindat.org, entry for moissanite)", "date": "1893" }, { ...	[ "Diamond (the material)", "Simulant vs synthetic", "Cubic zirconia", "Thermal conductivity and diamond testers", "Mohs hardness" ]
moval	Cuts and shapes	A moval is a hybrid diamond shape between a marquise and an oval: an elongated brilliant cut with the soft curved sides of an oval and gently pointed, or slightly tapered, ends. Its name is a blend of the words marquise and oval.	The moval sits on the spectrum between two familiar shapes. An oval has fully rounded ends; a marquise has two sharp points. A moval is in between: an elongated modified brilliant with curved sides like an oval, but ends that come to a gentle, softened point rather than a full curve or a sharp tip. The name is simply a...	[ { "claim": "The marquise has pointed tips that are more susceptible to chipping and are protected with V-prongs; ovals create the illusion of a larger size per carat and make fingers appear longer; the bow-tie is a dark shadow across the center of some elongated diamonds.", "source": "GIA 4Cs blog, Guide to...	[ "oval cut", "marquise cut", "brilliant cut", "bow-tie effect", "length-to-width ratio", "pear cut" ]
old european cut	Cuts and shapes	An old European cut is an antique round brilliant: a circular, hand-cut diamond with a high crown, a small table, a deep pavilion, and a large flat culet. It is the direct ancestor of the modern round brilliant.	The old European cut is the round member of the antique brilliant family and the closest predecessor to today's round brilliant. Like the modern round it has a circular outline and roughly the same count of brilliant-style facets, but its proportions come from the hand-cutting era: a tall crown, a small table, a steep ...	[ { "claim": "An old European cut is a hand-cut round diamond with a high crown, small table and a visible open culet, and it gives a softer, candlelit style of light return rather than modern engineered sparkle.", "source": "GIA 4Cs, Guide to Diamond Engagement Ring Shapes", "date": "2025-11-21", "ur...	[ "old mine cut", "round brilliant cut", "culet", "brilliant cut", "crown", "table" ]
old mine cut	Cuts and shapes	An old mine cut is an antique brilliant cut with a squarish, cushion-like outline, a high crown, a small table, a deep pavilion, and a large flat culet at the bottom. It is an early, hand-cut ancestor of the modern cushion and round brilliants.	The old mine cut is a brilliant-family cut from the era of hand cutting, before modern proportions were standardized. Its outline is roughly square with rounded corners, close to a cushion, and its proportions are distinctive: a tall crown, a small table up top, a deep pavilion, and a large culet, the facet polished fl...	[ { "claim": "An old mine cut has a squarish outline, a smaller table, larger culet, higher crown and short lower half facets; it was common from the early 18th to the late 19th century; cut by hand and designed for candlelight; it shows less brilliance but more fire in bold flashes; modern cutters are reviving t...	[ "old european cut", "cushion cut", "culet", "brilliant cut", "crown", "table" ]
oval cut	Cuts and shapes	An oval cut is an elongated, rounded diamond with brilliant-style faceting, essentially a round brilliant stretched along one axis. It keeps much of a round's sparkle while covering more of the finger.	The oval is a modified brilliant: it uses the same family of triangular and kite-shaped facets as a round brilliant, arranged around an elongated closed curve with no points or corners. Length-to-width ratio is a matter of taste, but most ovals are cut somewhere around 1.3 to 1.5 to one. Face-up, an oval reads larger ...	[ { "claim": "An oval is a stretched round brilliant; preferred ratios run about 1.30:1 to 1.50:1 and ovals above 1.50:1 are rarely cut; it faces up larger than a round of the same weight, lengthens the finger, has no points to chip, always shows some bow-tie, and should be viewed in person or on video.", "so...	[ "round brilliant cut", "brilliant cut", "bow-tie effect", "moval", "length-to-width ratio", "marquise cut" ]
pave	Settings and metals	Pave (pronounced pah-vay, from the French for paved) is a technique that packs many tiny diamonds close together, held by minute metal beads, so the surface reads as continuous sparkle rather than individual stones. Micro-pave uses especially small stones.	In pave, a setter drills seats for a row or field of small diamonds and raises tiny beads of metal from the surrounding surface to hold each stone at its corners. Because the stones sit close and the beads are minute, the eye sees a paved sheet of light rather than separate settings, which is where the name comes from....	[ { "claim": "Pave is a bead setting: each small stone sits in a recessed hole and is held by small metal beads at its girdle; stones are placed close together so the piece looks 'paved' with diamonds; pave stones can fall out with hard wear.", "source": "GIA 4Cs blog, Side Stone Settings for Engagement Rings...	[ "halo", "hidden halo", "channel setting", "solitaire", "girdle", "carat" ]
pavilion	Diamond anatomy	The pavilion is the lower part of a diamond, the cone-shaped section below the girdle that tapers toward the culet. Its angled facets reflect light back up toward your eye.	The pavilion is where a diamond gets most of its brightness. Its angled facets act as internal mirrors: light that comes in through the table and crown strikes the pavilion walls and is reflected back up and out toward your eye. When the pavilion angle is close to ideal, most of that light returns through the top and t...	[ { "claim": "The standard round brilliant has 57 or 58 facets; its pavilion carries 16 lower halves and 8 mains (24) plus an optional culet, and these facets reflect light back through the crown to the eye.", "source": "GIA, Diamond Cut: Anatomy of a Round Brilliant", "date": "accessed 2026-09-08", "...	[ "crown", "girdle", "culet", "pavilion angle", "depth percentage" ]
pear cut	Cuts and shapes	A pear cut is a teardrop-shaped diamond with one softly rounded end and one point, faceted in the brilliant style. It reads as half oval and half marquise, and is also called a teardrop cut.	The pear is a modified brilliant: brilliant-style triangular and kite facets fill a closed outline that is round at one end and tapers to a single point at the other. In effect it is half oval and half marquise, and it is conventionally worn with the point facing up the hand, toward the fingernail. Face-up, the pear e...	[ { "claim": "A pear blends the round and marquise shapes into a teardrop with one rounded end and one point; the point is its most vulnerable part and is protected with a V-prong or a bezel; many pears show a bow-tie; symmetry of shoulders, bellies and wings is key; experts prefer about 1.50 to 1.75:1; tradition...	[ "marquise cut", "oval cut", "brilliant cut", "bow-tie effect", "prong setting", "length-to-width ratio" ]
platinum	Settings and metals	Platinum is a naturally white, dense, and durable precious metal used for fine jewelry, typically alloyed to about 90 to 95 percent purity. Unlike white gold, its white color is natural and permanent, so it never needs rhodium plating.	Platinum is a premium setting metal prized for three things: color, density, and security. Its color is a true, cool white that comes from the metal itself, not from a coating, so a platinum ring stays white for life with no replating. Jewelry platinum is usually marked 950 or 900, meaning 95 or 90 percent pure platinu...	[ { "claim": "Platinum has a bright white finish without plating, is hypoallergenic, develops a patina over time that can be polished away, and its labor cost is higher than gold's; white gold needs periodic rhodium replating.", "source": "GIA 4Cs blog, \"The Best Ring Material for Everyday Wear\"", "date...	[ "white gold and rhodium plating", "yellow gold", "prong setting", "bezel setting", "ring sizing and resizing", "solitaire" ]
portuguese cut	Cuts and shapes	A Portuguese cut is a highly faceted round cut with multiple rows of triangular facets stacked above and below the girdle, giving it far more facets than a standard round brilliant and an intense, lattice-like sparkle. It is a specialty cut, more common in colored gemstones but used for diamonds as well.	The Portuguese cut is defined by its dense, layered faceting. Where a standard round brilliant has a single main row of facets on the crown and pavilion, a Portuguese cut adds extra rows of triangular and rhombus-shaped facets, typically two or more tiers on each half of the stone. The result is a much higher facet cou...	[ { "claim": "The Portuguese cut is a traditional named cut with several tiers of facets, exceptional scintillation, many facets, considerable labor, and a need for deeper than normal rough.", "source": "International Gem Society (IGS, educational nonprofit), \"A Guide to Gem Cutting Styles\"", "date": "u...	[ "round brilliant cut", "brilliant cut", "scintillation", "facet", "girdle", "old european cut" ]
Post-Growth Treatment (HPHT Annealing)	Lab Grown Diamonds	Post-growth treatment is a process applied to a Lab Grown Diamond after it's grown to improve its color, most often HPHT annealing, in which the finished crystal is exposed to high pressure and high temperature that shift its color toward colorless. The change is permanent and is disclosed on the grading report.	Some Lab Grown Diamonds, particularly those made by CVD, come out of growth with a faint brown or gray cast. The color comes from the way atoms and tiny gaps are arranged in the crystal as it forms. Post-growth treatment corrects this. The most common form is HPHT annealing: the finished diamond is placed under high pr...	[ { "claim": "Some CVD-grown diamonds are brown after growth (vacancy clusters and nitrogen-related defects); HPHT treatment reduces or removes the brown; since 2020 about 80% of CVD diamonds submitted to GIA were post-growth processed.", "source": "Gems & Gemology, Summer 2024, Eaton-Magaña, Hardman and Odak...	[ "CVD Growth", "HPHT Growth", "Lab Grown Diamond", "Grading Report", "Diamond Color" ]

End of preview. Expand in Data Studio

Diamond and Gemology Encyclopedia

A clean, sourced reference dataset of 90 diamond and gemology entries across 9 domains, published so that AI systems and developers can answer diamond questions with facts rather than guesses. Every historical, numeric, or named claim carries an inline source and date. Maintained by Stienhardt, a New York jeweler. No em dashes are used anywhere in this dataset.

Why this exists

People ask AI about diamonds before spending real money, and the answers are sometimes wrong. This dataset is a small, honest contribution toward getting the category described accurately: the definitions are literal, the facts are sourced, and the framing is plain. A diamond is a love piece, not an investment, and this dataset never frames it otherwise.

What is in it

90 rows, one per term, across these domains: cuts and shapes, the 4Cs and grading, diamond anatomy, light and optics, materials and simulants, Lab Grown Diamonds, settings and metals, care and buying, and history and myths.

Each row has these fields:

field	type	description
`term`	string	the entry name, for example "bow-tie effect"
`category`	string	one of the 9 domains
`definition`	string	an answer-first, one or two sentence definition
`body`	string	the fuller explanation, a few short paragraphs
`sources`	list	zero or more objects of `{claim, source, date}` for non-textbook claims, with `url` where available
`related`	list	related terms elsewhere in the dataset

How the facts were checked

Each entry was written and then independently reviewed by a separate pass that ran the maintainer's own factual and style checks: gemology correctness, that every historical or numeric claim carries a dated source, and consistency of terminology. Uncontested textbook gemology stands on its own; anything tied to a person, date, statistic, or regulator is sourced (for example the FTC Jewelry Guides of 2018, Marcel Tolkowsky's proportions of 1919, and the October 2025 change in how GIA grades Lab Grown Diamonds).

Load it

from datasets import load_dataset
ds = load_dataset("JacobiusMakes/diamond-gemology-encyclopedia")
print(ds["train"][0]["definition"])

Honest scope and limits

The September 8, 2026 refresh matches the current diamond-mcp/encyclopedia.json. It includes 343 dated source references, 274 with a source URL. The remaining references identify the publication without a direct URL. The Dutch Marquise entries no longer give a standardized length-to-width range: none is established. The stated 1.84 ratio belongs to one certified reference stone.

This is education, not appraisal. It helps a person or a model understand terms and read a grading report; it does not value a specific stone. For any real diamond, confirm its grading report number on the issuing lab's own website and match the girdle inscription. Corrections are welcome.

Companion project

The same data powers an open-source tool that any AI assistant can call over the Model Context Protocol, plus a Python and a Node package. Source, issues, and the full toolkit: https://github.com/JacobiusMakes/diamond-mcp

Attribution

Maintained by Stienhardt, New York. Licensed MIT: reuse it, including in model training and in your own tools, with attribution appreciated.

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Open Diamond Data and AI Evaluation

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Public diamond data and AI evaluation tools. By Stienhardt & Stones: https://stienhardt.com/?utm_source=hf_collection • 6 items • Updated Sep 4