Whether it’s understanding gemological or jewelry terms in an article you’re reading or simply gaining a greater understanding of the world of jewelry and gemstones, our Jewelry & Gem Dictionary is a handy reference guide. And, unlike most dictionaries, ours makes for interesting reading all on its own!

THE 4 C’s
Standardized form of grading diamonds, based on the qualities of Carat, Clarity, Color, and Cut.

A cabochon is a stone that has a rounded, domed surface with no facets. A cabochon garnet is also called a carbuncle.

Cairngorm is a yellow-brown type of smoky quartz that is often used in traditional Celtic jewelry. Cairngorm is not Scottish topaz. The supply of cairngorm is virtually exhausted, so heat-treated Brazilian amethyst is used as a substitute in Scottish jewelry.

Calcite (Calcium Carbonate, CaCO3) is a very common mineral that comes in a wide variety of forms, shapes and colors. The trigonal crystals range from translucent to transparent. Transparent calcite exhibits a double refraction effect (when you look through the crystal, singel items are doubled). Calcite has a hardness of 3 (most forms), a specific gravity of about 2.7, a refractive index of 1.49 and 1.66, and a white streak.

Calibre-cut stones are small stones that are cut into special shapes that are meant for use in commonly-used designs. These stones usually have step-cut facets and are generally rectangular shaped.

A California ruby is actually a pyrope garnet (and not a ruby at all).

A cameo is a relief carving (a carving that comes up above the surface) on a shell or stone. In multi-colored cameos, a layered substrate is used (with two different colors), and when part of the upper layer is carved away, the second color emerges as the background. Cameos are frequently portraits of women. Many imitation cameos are made from pressed glass or plastic; some of these use two different colors.

A cameo habille (meaning “dressed cameo” in French) is a “jewel within a jewel,” a cameo in which the subject carved in the cameo (usually a woman) is wearing a miniature piece of jewelry (like a tiny diamond necklace with a stone embedded in the cameo).

Canary diamonds are diamonds that have a deep yellow color. Diamonds are precious, lustrous gemstones made of highly-compressed carbon; they are one of the hardest materials known. Diamonds have a hardness of 10, a specific gravity of 3.5, and a refractive index of 2.417 – 2.419

Cape amethyst is a form of amethyst that is layered or striped with milky quartz. Cape amethyst is a translucent gemstone that ranges from light- to medium-purple and has white bands.

A carat (ct.) is a standard measure of weight used for gemstones. One carat weighs 0.2 gram (1/5 of a gram or 0.0007 ounce). A hundredth of a carat is called a point. The carat unit was introduced in 1907. Diamond carats are determined by weight, whereas cubic zirconia (CZ) carat weights are actually based on dimensions. A 5 carat CZ, for example, is the same width and length as a 5 carat diamond, but weighs much more. One of the 4 Cs used to grade diamonds.

A carbonardo is a rare type of opaque black diamond; they are not used for jewels, but for items like drilling bits and abrasive wheels. They were once thought to have been formed as a result of a comet impact 2 billion years ago, but this is no longer thought to be true. The largest diamond ever found was a carbonardo that weighed over half a kilogram. Carbonadoes are found in Bahia, Brazil, South America. Unlike other diamonds, carbonadoes are not found in a crystallized form – they are found in irregular or rounded fragments. Carbonadoes have a hardness of 10 and a specific gravity (density) of 3.1-3.3. Diamonds have a very hard polycrystalline carbon structure.

A carbuncle is a cabochon garnet.

Carnelian (also called cornelian and carneole) is a reddish form of chalcedony (a type of quartz). This translucent stone has a waxy luster. The best carnelian is from India. Most commercial carnelian is really stained chalcedony. Carnelian has a hardness of 7 and a specific gravity of 2.61.

Casting is the process in which metal is shaped by melting it and pouring it into a mold. This process has been used for thousands of years. Molds are made from many materials, including plaster compounds. Some different methods of casting include the lost wax process, centrifugal (or investment) casting, and sand casting.

A cathedral ring setting is a simple band that arches when seen from the side (like the arches of a cathedral).

Cat’s eye (chatoyant chrysoberyl) is a yellow to green-yellow to gray-green stone with a bright, pupil-like slit that seems to move slightly as the stone is moved. Most Cat’s eye is cut as cabochons to maximize the distinctive pupil-like effect. Most cat’s eye chrysoberyl is found in Brazil. Cat’s eye chrysoberyl has a hardness of 8.5. This stone is sometimes enhanced by irradiation (this process improves the color and accentuates the stone’s asterism).

Celtic jewelry was made by the Celts in Ireland, Wales, Scotland, and Brittany. The Celts used bronze, silver and gold in their jewelry and stones like cairngorm and amethyst. Circular brooches with a long, hinged pin, called penannular brooches, date from ancient times. The earliest-known piece of Celtic jewelry is the Hunterston brooch from 700 A.D.

The central, dominant stone in a piece of jewelry set with multiple stones. In a ring set with one stone, the center stone is also called the solitaire.

CFW is an abbreviation for cultured freshwater pearls.

Chalcedony is a family of minerals (microcrystalline quartz) that are often milky to gray to bluish in color. Chalcedony includes agate, carnelian (waxy red), chalcedony (blue), chrysoprase (green), onyx (black and white), bloodstone, sard (brownish-red), jasper (hornstone), seftonite, and others. Chalcedony is porous and translucent. Chalcedony has a hardness of 6.5-7 and a specific gravity of 2.6.

(meaning sunken enamel) Champleve (also called email champleve) is a method of applying enamel to metal in which the design is first outlined on the metal surface by cutting lines into the surface. The engraved grooves are then filled with enamel, then fired to a glassy sheen, and polished. Champleve is similar to cloisonne, but not as delicate.

Grandiose dangle earrings that feature tiers of gemstones and/or detailing, for a glamorous evening look.

Channel set jewels rest in a metal channel, held in only by a slight rim which runs along the edges of the channel. Channel set jewels are usually round or baguette shaped.

Charel is a mark of relatively rare, medium-quality costume jewelry made by the Charel Jewelry Company, Inc. of Brooklyn, New York. Many Charel pieces have pastel-colored plastic stones on plated metal.

Charms are tiny, representational ornaments that are worn on bracelets and necklaces.

Jewelry featuring small dangling charms, which sometimes have symbolic or personal meaning. The charms can be mixed and matched to create a variety of looks.

Chasing is a type of metal decoration in which the metal is manipulated using a hammer and a punch, resulting in an effect similar to engraving or embossing.

A chaton is a stone with a reflective metal foil backing.

A chaton setting (also called coronet or arcade setting) is one in which the stone is held in by many metal claws around a metal ring.

Chatoyancy is the lustrous, cat’s eye effect seen in some cabochon stones, like cat’s eye, tiger’s eye (pictured above), and sometimes in other stones, like aquamarine. In chatoyancy, light is reflected in thin bands within the stone. Chatoyant stones are cut in cabochon to maximize the lustrous effect.

It is the chemistry of a gem material which is ultimately responsible for all of its physical properties. Chemistry determines color which in turn determines value. Heat treatment is a chemical modification of a gem material to improve its color and value.

Chenier is fine, hollow tubing that is used in the production of some jewelry findings (like clasps and joints), and lately, in the actual production of jewelry. The hollow tubes are lightweight and save in the use of gold. The tubes are hard to bend when they are empty, so a metal rod is inserted before bending, facilitating the bending.

A choker is a type of necklace that fits tightly around the neck. Chokers are from 14″ to 16″ in length, and were once only made of pearls. However, any necklace this size is now considered a choker.

Chrome diopside is an emerald-green colored gemstone. It is a chromium-rich variety of the common mineral diopside (Calcium magnesium silicate). Chrome diopside has a hardness of 5 to 6 and a specific gravity of 3.3 to 3.6.

Chromium is a hard, shiny, gray-white metal. This metal resists corrosion very well and is used in costume jewelry as a coating over other metals.

Chrysoberyl is a hard stone that ranges in color from yellow, to brown, to green. Some chrysoberyls include alexandrite and cat’s eye.

Chrysolite is a name used for many stones. During Victorian and Edwardian time, it referred to green-yellow chrysoberyl. It can also refer to peridot. Long ago, the name was used to refer to almost any yellowish gem.

Chrysoprase is the most valued variety of the mineral chalcedony (microcrystalline quartz) that contains nickel, giving it an apple-green color. Chrysoprase is porous and translucent. It is usually cut as a cabichon, and has been used since ancient times. Chrysoprase has a hardness of 7 and a specific gravity of 2.6. Chrysoprase is mined in Australia, Russia (the Ural Mtns.), Brazil, and the western USA. Chrysoprase is sometimes called “Australian jade,” but it is not related to jade. Hard-to-detect imitation chrysoprase is made by staining agate with chromium salts.

Cire perdu (French for “lost wax”) is a process of casting metal in which the original model is sculpted in wax. The wax is entombed in clay, and the wax is then melted out, producing a hollow mold. The mold is then filled with molten metal. The clay is broken off and the cast metal remains.

Citrine (from the French for “lemon”) is a rare, yellow type of quartz, a semi-precious stone that ranges in color from pale yellow to orange to golden brown. The best quality citrine is found in Brazil. Many of the stones sold as citrine are actually heat-treated amethysts. Citrine has a hardness of 7 and a specific gravity of 2.65.

Clarity is the clearness of a gemstone, or the lack of internal flaws. The clarity scale for diamonds runs from FL (flawless, with neither internal nor external flaws), to I3 (having many clearly visible imperfections using only the naked eye). A ten-power loupe is used to examine a diamond for clarity. Traditionally used to grade diamonds, this term also refers to the brilliance of any stone. One of the 4 Cs used to grade diamonds.

A clasp is a fastener that can open and close, attaching two things together (for example, the two ends of a necklace, or a pin to a garment). The clasp on a piece of jewelry can tell you a lot about the piece, including giving an indication of its age (by determining when that particular type of clasp was invented and looling at the wear on the clasp), its quality (better quality pieces generally have better-quality clasps), and its composition and manufacturer (the clasp is often where the maker’s stamps are). For example, the spring ring clasp was invented early in the 1900’s; jewelry made prior to 1900 or so will not have a spring ring clasp. Some other common clasps include the lobster claw clasp, the box clasp, the barrel clasp, the fold-over clasp, the hook-and-eye clasp, and the bar and ring toggle clasp.

A claw is a metal prong that holds a stone securely in a setting.

A claw setting is one in which a series of metal prongs (called claws) holds a stone securely in a setting (the claws grips the stone just above the girdle of the stone), with no metal directly under the stone (it is an open setting). This setting lets light in under the stone, so this type of setting is usually used for transparent, faceted stones. The modern-day claw setting became popular in the 1800’s.

Cleavage is the natural in which way a mineral breaks, along certain planes based on its internal crystalline structure.

Earrings for non-pierced ears.

Cloisonne is a method of applying enamel to metal in which the design is first outlined on the metal surface using a metal wire. The space between the wires is filled with enamel and then fired to a glassy sheen.

A closed setting is one in which the back of the stone is not exposed (the metal is not cut away behind the stone).

A cloud is a type of inclusion in some gemstones that has a milky appearance (and greatly affects the value of the stone). A cloud is usually composed of a cluster of tiny inclusions.

A cluster setting is one in which small stones or pearls are set around a larger stone.

A large ring that often features high CARAT stones and/or elaborate detailing. Applies to any ring that is elegant and dramatic enough to be worn to a cocktail party.

A collet setting is a very early method of setting gemstones. A collet is a thin, round band of metal that goes all around the stone. One edge of the metal is crimped over the edges of the stone and the other edge is soldered to the metal of the jewelry, holding the stone in place. This closed setting sometimes also had metal claws along the outside to hold the stone even more securely (the claws were not used much after the 1200’s and 1300’s.

A collarette (also known as a bib necklace) is a short necklace with flowing ornaments at the front.

The color scale is used to describe the color tones of a gemstone. For diamonds, the color scale ranges from D, meaning completely colorless, to Z, which indicates a distinct yellow cast. As the scale moves from D to Z, it indicates increasing levels of yellow and brown tone. For color gemstones, the color is measured by tone and hue. Color is the most important criteria in determining the value of a colored gemstone. More important than clarity and cut, even subtle differences in hue can correspond with marked variations in valuations.

The rounded finish on the inside of a ring’s band. This design does not pinch the skin of the finger as much as other ring bands and provides comfort for constant wear.

A composite suite is a piece of jewelry that can be taken apart into two or more pieces which can also be worn. For example, a necklace may be disassembled into two bracelets.

Confetti lucite is transparent plastic with glitter or other small pieces of material within it. Whimsical bangles, earrings, pins, necklaces and other jewelry have been made from confetti lucite.

Copper is a soft metal often used in jewelry. It is used in making bronze, brass, and gold alloys.

Coral is an animal that grows in colonies in the ocean. Coral polyps secrete a strong calcium structure that is used in jewelry making. Coral ranges in color from pale pink (called angelskin coral) to orange to red to white to black. The most valued colors are deep red (called noble coral) and pink. In jewelry making, coral is either carved into beads, cameos, or other forms, or is left in its natural branch-like form and just polished. It used to be thought that coral protected the wearer, so it was a traditional gift to children. Coral has a hardness of about 3.5 and a specific gravity of 2.6 to 2.7. Since it is composed of calcium carbonate, coral will effervesce if touched with acid. Imitation coral is made from glass, porcelain, or plastic.

A coronet setting (also called ch?ton or arcade setting) is one in which the stone is held in by many metal claws around a metal ring.

Corundum is a very hard mineral (hardness 9); only diamond is harder. Corundum is called ruby or sapphire, depending on the color (which depends on which metallic oxides are present). In its rare pure form, corundum is colorless and called white sapphire. Rubies contain chromic oxide, blue sapphires contain titanium, yellow sapphires contain ferric oxide. Other impure forms are opaque. Corundum stones can produce beautiful asterisms. The word corundum comes from the Tamil word for ruby. Corundum has a specific gravity of 3.96-4.01.

Any jewelry made from faux gemstones instead of precious or semi-precious stones, and/or from materials other than gold, silver, or platinum.

A crimp bead is a soft, metal bead through which string (for a bracelet or necklace) is threaded; the crimp bead can be squeezed shut with a pliers to secure the end loops of the threading material fasteners onto the clasps.

The crown is the upper part of a gemstone.

Crown glass is glass that contains no lead oxide. Some fake rhinestones are made from crown glass.

The protective clear cover that fits over the watch dial. It can be made of mineral, synthetic sapphire, plastic, or acrylic material. The sapphire crystal is the most durable, as only a diamond can scratch its surface.

Crystal is high-quality glass containing at least 10% lead oxide. Lead added to the melt produces very clear glass resembling rock crystal. The process of making lead crystal was discovered by the English glassmaker George Ravenscroft in 1676. Crystal is colored by adding various metallic oxides to the melt. The hallmark of crystal is its exceptional brilliance and light refraction. Swarovski is considered the finest Austrian crystal.

A crystal is a solid whose atoms form a very regular structure. Some crystals include quartz, diamond, and emerald.

Crystal habit is the crystal form that a particular crystal has. The most common crystal habits:

Prismatic – elongated with parallel sides, like emerald, tourmaline
Tabular – short and flat (table-like), like morganite
Ocatahedral – eight faces, like diamond
Dodecahedral – 12 faces, like garnet
Acicular – needle-shaped, like rutilated quartz
Platy – occurring in very thin plates, like hematite
Crystals are divided into seven crystal systems, according to their optical properties (how light bends within the crystal), plane of symmetry, axis of symmetry, center of symmetry, crystallographic axis. Within each of the systems, the crystals can mineralize into different crystal habits (form). The seven crystal systems are: cubic systems, tetragonal systems, hexagonal systems, trigonal systems, orthorhombic systems, monoclinic systems, and triclinic systems. The study of this system is imperative to correctly determine and identify rough gem materials. For example, ammolite is of the orthorhombic system which is based on three unequal axes all at right angles to each other. As you look down one of the axes, two unequal axes crossed at right angles can be seen. A possible two-fold rotational symmetry is seen in the axes as well as two possible mirror planes that are parallel to the axes.

Cubic zirconia (also known as cubic zirconium) is an inexpensive, lab-produced gemstone that is generally cut to resemble diamonds. They can be colored to resemble other precious and semi-precious stones, and are a staple of high quality costume jewelry. Cubic zirconia was developed in 1977.

A cuff bracelet is a stiff, relatively wide bracelet. A type of bracelet which does not form a continuous circle – usually the two ends do not close completely. Made to be slipped on the side of the wrist instead of over the hand.

Cufflinks are men’s jewelry that close the buttonholes of the cuff of a long-sleeved shirt. Some cufflinks are basically two button-like objects connected by a chain; the bottons go through the cufff’s buttonholes. Another type of cufflink has a decorative button attached to a stick whose end swivels out to form a T-shape that goes through the buttonhole. Cufflinks were first worn in the 1800’s.

A culet is the bottom point of a gemstone or a small facet that is ground at the base of a brilliant-cut gemstone. The culet prevents splintering of the stone. Modern stones rarely have a faceted culet.

The Cullinan diamond (also called the Star of Africa) is the largest diamond yet found, weighing 3,106 carats (roughly 1.3 pounds) in its rough form. It was mined at the Premier Mine in South Africa in 1905. This enormous gem was named for the chairman of the company that owned the mine. It was given to King Edward VII of England for his birthday in 1907. The diamond was cut (by Joseph J. Asscher of Amsterdam) into many stones, including the Cullinan I (530 carats, pendelique-brilliant shaped, the largest cut diamond in the world), the Cullinan II (317 carats, cushion shaped), Cullinan III (94 carats, pendelique shaped), Cullinan IV (63 carats, square-brilliant shaped), and many other smaller stones.

Cultured pearls are pearls produced by oysters that have been surgically injected (nucleated) with bits of mussel shell. After 5-7 years, the oysters are retrieved and the pearls are harvested. This method of “manufacturing” pearls was invented in 1893 by Kokichi Mikimoto.

Cupid’s Darts is another name for rutilated quartz.

Cushion cut stones are shaped like a cushion – they have a squarish shape that is rounded on the edges. These stones usually have facets similar to those of a brilliant cut stone.

Refers to the geometric proportions of a gemstone. The cut of a gemstone is one of the most important factors in determining how much sparkle a gemstone produces.

Cut, Ideal
A diamond cut of perfect proportions, having depth percentages and table percentages that maximize fire and brilliance.

Cut, Very Good
A grade of diamond cut that fits very strict requirements for depth percentage and table percentage. These specific proportions maximize fire and brilliance in a diamond.

Cut, Good
The cut grade assigned to diamonds with acceptable proportions. These diamonds generally have very good brilliance and fire and they are also beautiful in jewelry.

Cut, Fair
The cut used to maximize the weight of a diamond, generally at the expense of fire and brilliance. Diamonds with this cut are less expensive than diamonds having good and very good cuts, and they lack the sparkle people expect from a diamond.

Cut, Poor
This cut makes diamonds appear lifeless. These diamonds are not recommended for jewelry.

Cut beads are glass beads that have been faceted. This process makes the bead reflect and refract more light.

Common cuts include the brilliant cut, old European cut, emerald cut, radiant cut, rose cut, step cut, pendelique cut. Mixed cuts in which the style of the facets above and below the girdle are different. Other, more unusual cuts, are know as fantasy cuts (like the heart cut).

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