Jewelry and Gemstone Glossary of Terms

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Cabochon

A stone which has been cut with a rounded convex surface and a flat base. It may be high domed or almost flat and can be cut in round, oval, square or freeform shapes. A cabochon has no facets. This is one of the oldest and simplest cuts. This form of cutting is most often used on stones like turquoise, lapis, opals, various forms of quartz and other opaque and semi-opaque stones which may be cut either freeform or calibrated.

Sometimes, lower quality stones such as ruby, amethyst, citrine and garnet are also cut en cabochon. By their nature, stones like drusy cannot be domed or polished and it is now common to call any stone that is not faceted a cabochon. (pronounced:cab-uh-shon)

Calibrated

A calibrated stone is one that has been cut exactly to a standard size, i.e. 5 mm, 10 mm x 14 mm. Jewelers often purchase calibrated cabochons or faceted stones when the design requires two or more stones of the same exact size or when a design will be duplicated many times as in manufactured jewelry.

Cameo

Cameos are carvings traditionally done on shell or stone where the design is carved in relief with a contrasting colored background. This is the opposite of the intaglio. The most recognized cameos today are of florals and the head and shoulders of Victorian women but carvings of mythological gods and goddesses, scenes and military heroes were popular as far back as Green and Roman times.

Cameos have been collected and worn by many including Napoleon, Queen Elizabeth, Catherine the Great and Queen Victoria. Pope Paul II collected cameos and it has been noted in some historical references that because he wore so many heavy cameo rings his fingers were cold from lack of circulation and this ultimately may have influenced his death.

Carat

Carat (ct.) is the 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. Note that karat is the term used to describe the fineness of gold.

Carnelian

Carnelian is a form of chalcedony that ranges in color from red to orange. It is a translucent stone that may contain bands of color. This stone has been used to offer protection during travel and is thought to help with diseases of the blood including the relief of menstrual cramps. It is found in India, Australia, Brazil, Germany, Madagascar, Russia, South Africa, and the USA.

Cast or Casting

The process of making jewelry by pouring molten metal into a mold. Intricate patterns and shapes can be carved into wax from which the mold is made. This process is used to create one of a kind items and is used extensively to mass produce less expensive jewelry items.

Chalcedony

Chalcedony, pronounced kal-sed-uh-nee, is a micro crystalline member of the quartz family. It is found all over the world and is one of the oldest stones used by humans for decoration. It has a waxy luster and may be opaque as in jasper, petrified wood, and bloodstone or translucent to transparent in agate, carnelian, or chrysoprase. In the jewelry trade, the term chalcedony usually refers to white, gray, or blue translucent stones such as "Blue Chalcedony".

Other forms of chalcedony are onyx, sard, sardonyx, petrified dinosaur bone, chert, flint, fire agate and dendritic agate. Because it is a porous stone, it can be stained or dyed to enhance or change the natural color of the stone. Agates are often dyed while most onyx used for jewelry purposes is dyed black, thus the name "black onyx".

Charoite

Charoite is a fairly recent discovery found in Russia in 1978 in the Murun mountains in Yakutia, near the Charo River. This is the only known location for this rare mineral. It ranges in color from a light lilac to a deep purple and can be mottled with gray, white and black inclusions. The chatoyant variety in a bright deep purple, is usually considered more valuable than the non-chatoyant variety although both are used in jewelry and compliment a number of other stones.

Chatoyant

This term is applicable to a number of different stones, Tiger's Eye is one example. A chatoyant gem exhibits a changeable silky luster as light is reflected within the thin, parallel, fibrous bands. This effect is due to the fibrous structure of the material. (pronounced: cha-toy-ant)

Chrysocolla

An inexpensive, usually opaque, blue to blueish green mineral, Chrysocolla is most often cut as a cabochon for jewelry purposes but high quality, translucent stones know as "gem chrysocolla" are highly prized and can be considerably higher in cost. Another form is "drusy chrysocolla" where the base stone is covered with tiny clear quartz crystals and is often found in botryoidal form. Chrysocolla was also used by the ancient Greeks as an ornamental stone.

Often confused with turquoise, it is a copper bearing mineral found wherever copper deposits occur in Australia, Chile, Democratic Republic of Congo, England, Israel, France and Zaire with notable deposits Arizona, Utah, New Mexico and Pennsylvania in the USA.

Chrysoprase

A gemstone variety of chalcedony (a form of quartz) Chrysoprase contains small quantities of nickel which is responsible for its apple-green color. It is cryptocrystalline, which means that it is composed of very fine crystals that cannot be seen as distinct particles under normal magnification. Due to its comparative scarcity and unusual green color, chrysoprase is one of the most prized varieties of quartz and commands top dollar for quality stones.

Also spelled chrysophrase.

Citrine

Citrine is a variety of quartz ranging in colors of yellow, yellow-brown, orange, dark orange-brown, or reddish-brown. Brazil is the leading producer of naturally mined citrine, however, most commercial citrine on the market today is actually artificially heated amethyst or smoky quartz.

Citrine crystals may form together with amethyst or smoky quartz to form a BI-colored quartz called ametrine. The name comes from the French word for lemon, "citron".

Cloisonné

Cloisonné (pronounced kloi-zen-a) is a technique in which colors of a design are kept apart by thin metal strips.  Metal filaments are attached to outline the design. Then these areas are filled with colored enamel and heated at high temperatures to fuse the enamel to the surface.

It is believed that Cloisonné originated in Beijing during the Yuan Dynasty (1271-1368). The process was improved and advanced during the Ming dynasty (1426-1456) and further perfected during the Qing Dynasty (1736-1795).

Also, see enamel and plique-a-jour.

Cubic Zirconia

A man-made, synthetic stone used as an inexpensive alternative to a diamond or other colored stone. Note: Zircon is a natural gem which has no connection with cubic zirconia.

Culet

The bottom point of a faceted gemstone is called the culet. This tip may or may not be a facet.

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