The Glossary

GIA

Gemological Institute of America — the nonprofit that created the 4Cs (1953) and the modern diamond grading lab system. GIA reports are the global benchmark; AGS (acquired by GIA in 2022) is the equivalent for fancy cuts.

IGI

International Gemological Institute — the dominant lab for lab-grown diamond grading and a major player in colored stone certification. IGI-graded natural diamonds typically trade at a 3-8% resale discount to equivalent GIA-graded stones.

AGS

American Gem Society — laboratory created in 1996 specializing in cut grading via its 0-10 scale (AGS 0 = Ideal). Acquired by GIA in 2022 and folded into GIA's reporting system.

SSEF

Swiss Gemmological Institute — the auction-house preferred lab for high-value colored stones. SSEF and Gübelin reports add measurably to ruby, sapphire, and emerald resale prices at Sotheby's and Christie's.

Brilliant Cut

A cut style featuring 57 or 58 facets engineered to maximize light return and scintillation. The modern round brilliant — perfected by Marcel Tolkowsky in 1919 — remains the benchmark, accounting for roughly 75% of diamonds sold worldwide today.

Round Brilliant

The most popular diamond shape and the most expensive per carat. A 1.0 ct G/VS1 round brilliant resells for roughly $5,500–7,200 in 2026 — pricing that holds best on the secondary market.

Old European Cut

The predecessor to the modern round brilliant, cut roughly from 1890 to 1930. Characterized by a smaller table, taller crown, and circular girdle. Old European cuts are prized in vintage and Art Deco-era pieces; a 1.0 ct trades 15–25% below a modern equivalent.

Old Mine Cut

A cushion-shaped cut common from 1700 to the early 1900s, hand-faceted with a high crown and large open culet. Sotheby's records show old mine diamonds trading at 10–30% premiums to modern equivalents when set in original Georgian or Victorian mounts.

Emerald Cut

A rectangular step cut with cropped corners, originally developed for emeralds to relieve crystal stress and now equally iconic in diamonds. Step cuts show inclusions more obviously — always specify VS1 or better.

Asscher Cut

A square step cut developed in 1902 by Joseph Asscher in Amsterdam. The Royal Asscher Cut (patented 2001) adds 58 facets and a higher crown. Often misidentified as a square emerald cut — the cropped corners and X pattern are the giveaway.

Princess Cut

A square modified brilliant introduced commercially in 1980. Carat-for-carat it costs 15–25% less than a round brilliant — but the pointed corners are prone to chipping, so V-prong settings are essential.

Cushion Cut

A square or rectangular cut with rounded corners. Two families exist: 'chunky' (larger facets, more fire) and 'crushed ice' (smaller facets, more scintillation). The cushion is the most popular fancy shape for engagement rings in 2026.

Oval Cut

An elongated brilliant that maximizes finger coverage per carat — an oval looks roughly 10% larger than a round of equivalent weight. Length-to-width ratios of 1.35–1.50 are most desirable.

Marquise Cut

An elongated brilliant with pointed ends, commissioned by King Louis XV of France around 1745. Most efficient cut for face-up size per carat. The 'bowtie' effect — a dark band across the center — is the primary thing to evaluate.

Pear Cut

A teardrop-shaped brilliant cut, technically a hybrid of round and marquise. Length-to-width ratio between 1.55 and 1.75 is the editorial sweet spot. The most-requested cut for pendants.

Cabochon

A non-faceted polishing style with a smooth, domed top and a flat or slightly rounded back. Standard for opaque or asteristic stones — opals, moonstones, star sapphires, star rubies. The 'sugarloaf cabochon' (with a pointed dome) is the prized variant for Cartier vintage jewelry.

Briolette

A pear- or drop-shaped stone faceted across its entire surface, with no table or culet. Used primarily in earrings and pendants for maximum light play in motion. Notoriously difficult to set — requires drilled holes through the upper tip.

Love Bracelet

Cartier's screw-locked oval bracelet designed by Aldo Cipullo in 1969. Originally given only as a pair (one each by lovers) — modern editions are individually sold. The single most-tracked piece in the pre-owned market.

Juste un Clou

Cartier's nail-shaped bracelet and ring collection, also designed by Aldo Cipullo (1971). Reintroduced in 2012 and now Cartier's second-best-selling bracelet line after the Love.

Alhambra

Van Cleef & Arpels' four-leaf clover motif, launched in 1968. Five sub-collections (Vintage, Magic, Sweet, Pure, Byzantine) and the most counterfeited luxury jewelry design in the world. Mother-of-pearl Vintage Alhambra is the resale benchmark.

Serpenti

Bulgari's snake-motif collection, launched in 1948 as a wraparound bracelet-watch and expanded into a full jewelry line (Serpenti Viper, Serpenti Tubogas). Zendaya's red-carpet appearances drove a measurable resale lift starting 2021.

Trinity

Cartier's three-band rolling ring in yellow, white, and rose gold, designed by Louis Cartier in 1924. Originally a custom commission for Jean Cocteau. The single most accessible Cartier piece — current retail $1,860 and resells at 75-80% of new.

B.zero1

Bulgari's spring-coiled ring collection, launched 1999 and inspired by the Colosseum. Available in 1-band, 3-band, 4-band, and 5-band variants — the 4-band is the resale value leader.

Collier de Chien

Hermès' studded bracelet (and original 19th-century dog collar) reimagined for jewelry. The 'CDC' bracelet in 18k rose gold with diamond studs is one of the very few pieces that trades above retail on the secondary market.

Art Deco

The 1920s–1930s design movement defined by geometric forms, platinum mounts, and contrast color combinations (sapphire-and-diamond, ruby-and-onyx). Cartier's Art Deco pieces consistently set auction records — the 1928 Cartier 'Tutti Frutti' bracelet sold for $1.34M at Christie's in 2014.

Edwardian

Roughly 1901–1915, named for King Edward VII. Characterized by platinum filigree, garland motifs, and pearl-and-diamond combinations. The 'lace in platinum' aesthetic.

Art Nouveau

Roughly 1890–1910 movement emphasizing natural forms, flowing lines, and enamel work. René Lalique is the defining maker. Plique-à-jour enamel reached its peak in this era — and almost no contemporary maker can replicate it.

Victorian

1837–1901, spanning Queen Victoria's reign. Subdivided into Early/Romantic (gold, sentimental), Mid/Grand (mourning jewelry, jet), and Late/Aesthetic (silver, Japanese influence). Mourning jewelry is the most collected sub-category.

Retro

The 1935–1950 era defined by oversized, bold, three-dimensional gold pieces — the wartime response to platinum rationing. Van Cleef & Arpels' Ludo bracelets and Cartier's Tank watches are the era's iconic outputs.

Platinum

A naturally white, hypoallergenic metal typically 950 parts pure (PT950 hallmark). 60% denser than 18k gold and approximately 30 times rarer. Develops a soft patina with wear — connoisseurs prize this; collectors who want bright finish should re-polish every 18–24 months.

18k Gold

75% pure gold alloyed with 25% other metals (typically copper, silver, palladium). The European luxury standard — Cartier, Van Cleef, and Bulgari fine jewelry are all 18k. Hallmarked '750' under the international convention.

Yellow Gold

18k gold alloyed with roughly equal parts silver and copper. The traditional luxury choice and currently in a cyclical revival after a decade of rose-gold dominance.

Rose Gold

18k gold alloyed with higher copper content (≈22.5%) for a pink hue. Reached peak popularity 2014–2019; Cartier rose-gold Love bracelets still command the highest resale premium of any Love reference.

White Gold

18k gold alloyed with white metals (palladium or, historically, nickel) and finished with rhodium plating for brightness. The plating wears off every 12–24 months and requires re-rhodiuming.

Rhodium

A platinum-group metal applied as a thin electroplated layer to white gold for a bright reflective finish. Rhodium plating wears off — re-rhodium service costs $50–$120 at most jewelers.

14k Gold

58.3% pure gold — the U.S. consumer-jewelry standard but rarely used by European luxury houses. Acceptable for designer brands like David Yurman in select collections; not used by Cartier, VCA, or Bulgari for fine jewelry.

Prong Setting

Small metal claws that grip the stone — typically 4 or 6 prongs for round brilliants, 6 being the most secure. Tiffany's six-prong solitaire (introduced 1886) is the prong-setting reference standard.

V-Prong

A V-shaped prong wrapped around a stone's pointed corner — essential for protecting princess, marquise, and pear-cut stones from chipping. The single most important setting choice for pointed-corner cuts.

Bezel Setting

A thin metal collar that wraps the stone's girdle, holding it in place with no prongs. More secure than prongs and snag-free — ideal for active wearers. Slightly diminishes apparent brilliance because less light enters the pavilion.

Pavé

From the French 'paved' — small diamonds (typically under 0.02 ct each) set so close together the metal nearly disappears. Bvlgari's Serpenti Viper line and Cartier's iconic Panthère pieces showcase micro-pavé at its peak.

Micro-Pavé

Pavé using diamonds smaller than 0.01 ct (under 1.3mm), requiring a microscope to set. Differentiates haute joaillerie from production pavé — Van Cleef & Arpels and Graff are the benchmarks.

Channel Setting

A row of diamonds set in a metal channel with no prongs visible — the metal walls hold the stones via their girdles. Standard for eternity bands and Tiffany's HardWear collection.

Halo Setting

A ring of small diamonds encircling the center stone, making the stone look 25–40% larger. Most popular engagement style of the 2010s — now overshadowed by solitaires as the 'quiet luxury' aesthetic returns.

Tension Setting

A modernist setting where the diamond appears to float between two compressed metal bands. Requires platinum or 18k white gold for sufficient spring force. Niessing pioneered the genuine tension setting in 1979 — most 'tension-look' settings are actually channel-set illusions.

Plique-à-Jour

An enameling technique resembling stained glass — translucent enamel held in metal cells with no backing. Reached its peak in Art Nouveau pieces by René Lalique and Eugène Feuillâtre. Extremely fragile and almost extinct as a contemporary technique.

Tiffany Setting

Charles Lewis Tiffany's 1886 six-prong solitaire that lifted the diamond above the band to maximize light return — the design that effectively invented the modern engagement ring. Still produced and still the resale benchmark.

The 4Cs

GIA's 1953 grading framework: Cut, Color, Clarity, and Carat weight. Cut has the largest impact on visible brilliance and the highest impact on resale — never compromise on cut grade.

Carat

A unit of mass for gemstones equal to 200 milligrams. Diamond pricing follows non-linear 'magic-size' jumps at 0.5, 1.0, 1.5, 2.0 ct — a 0.95 ct stone resells for 15–20% less than a 1.0 ct of equivalent grade.

Color Grade

GIA's D–Z scale measuring a diamond's body color. D, E, F are colorless; G, H, I, J are near-colorless and offer the best resale value-per-dollar. Anything K or lower visibly yellows in white-metal settings.

Clarity Grade

GIA's 11-step inclusion scale from FL (Flawless) to I3. VS1 and VS2 are the value sweet spot — eye-clean, but not paying for invisible perfection. SI1 stones can be eye-clean depending on inclusion location.

Fluorescence

A diamond's tendency to glow (typically blue) under UV light. Faint and medium fluorescence are commercially neutral. Strong blue fluorescence in D-F colors trades at a 5-15% discount but can mask a yellowish tint in J-L colors — a contrarian value play.

Ruby

Red corundum — the same mineral species as sapphire. Burmese (Mogok) origin commands a 3–10× premium over Mozambique or Madagascar. 'Pigeon's blood' red is the prized color descriptor.

Sapphire

Corundum in any color other than red. Kashmir sapphires (mined 1881–1938) command the highest auction premiums; cornflower blue Ceylon and royal blue Burmese are next. Heat treatment is the norm — unheated specimens command 30–50% premiums with lab certification.

Emerald

Green beryl colored by chromium or vanadium. Colombian (Muzo, Chivor) origin is the benchmark. Nearly all emeralds are oiled to improve clarity — declaring 'no oil' on a GIA report adds significant value.

Paraíba Tourmaline

An electric blue-to-green copper-bearing tourmaline first discovered in Paraíba, Brazil, in 1989. Per-carat prices for Brazilian Paraíba reach $30,000+ in fine clean stones — among the highest in the gem trade.

Akoya Pearl

Cultured saltwater pearl from Pinctada fucata oysters, produced primarily in Japan. Typically 6–8mm, with the highest luster among cultured pearls. Mikimoto's standard offering.

South Sea Pearl

Cultured saltwater pearls from Pinctada maxima oysters in Australia, Indonesia, and the Philippines. Largest of all cultured pearls (typically 10–15mm). White and golden varieties; the deep gold from Philippine production is most prized.

Tahitian Pearl

Naturally dark cultured pearls from Pinctada margaritifera oysters in French Polynesia. Colors range from charcoal grey to true black with green, blue, or aubergine overtones. The peacock-overtone Tahitian is the auction benchmark.

Mohs Hardness Scale

Friedrich Mohs' 1812 scale of scratch resistance from 1 (talc) to 10 (diamond). Sapphire and ruby are 9; emerald is 7.5–8 and chips easily despite its hardness rating. Anything below 7 is too soft for daily-wear ring settings.

Scintillation

The visible flashes of light a diamond produces when it (or the light) moves. Distinct from 'fire' (rainbow colors) and 'brilliance' (white-light return). Excellent-cut round brilliants maximize all three.

Fire

The spectral (rainbow) colors a diamond disperses through its facets. Highest in cuts with steeper crown angles — old European cuts and cushions show more fire than modern rounds, which prioritize scintillation.

Asterism

The star effect visible in certain cabochon-cut sapphires, rubies, and rose quartz — caused by needle-like inclusions reflecting light. Six-rayed stars are most common; twelve-rayed stars are exceptionally rare.

Mêlée

From the French 'mixture' — small diamonds typically under 0.20 ct used in pavé, channel, and accent settings. Lab-grown mêlée increasingly appears in production jewelry; reputable houses disclose it.

Hallmark

An official stamp verifying precious-metal purity. The French eagle's head (since 1838) certifies 18k gold; the Italian 750 mark plus a maker's number does the same. UK hallmarks include the assay office mark, date letter, and metal purity.