The cabochon cut numbers among the so-called "smooth cuts" in which the smooth surface of the stone is not subdivided into facets. Also known as the "mugel cut," the cabochon is the oldest known cut for gems. Connoisseurs differentiate between ball-shaped cabochons, which resemble a prone hemisphere in side view, and conical cabochons, which rise steeply to a rounded point in side view.

The word "carat" is also sometimes spelled with a "K" but is always abbreviated "ct". The carat has been used since classic antiquity as the unit of weight for jewelry stones and pearls. Carat, as a unit of weight, should not be confused with "carat" as a degree of purity for gold alloys. Both words are derived either from the Greek word "keration" (the fruit of the carob tree) or from the kuara seed of the African coral tree. One metric carat weighs 0.2 grams. Jewelry aficionados are particularly interested in the weight, i.e. the number of carats, of diamonds. A legendary type of diamond is the "one carat": i.e. a diamond measuring 6.5 mm in diameter and weighing exactly 0.2 grams. A "half carat" measures 5.2 mm in diameter. A "two carat" is 8.2 mm in diameter.

The carré cut, also known as square cut, is a quadratic shape for transparent gemstones. Its quadratic table is usually surrounded by a terraced border consisting of two rows of facets.

Diamond jewelry (solitaires starting at 0.25 carats, pavé starting at 0.50 carat) from Wempe Jewelers are accompanied by certificates, i.e. documents containing the most important items of information about the pieces. The individually drafted certificates of authenticity that accompany each piece of diamond jewelry from Wempe Jewelers above all certify the quality of the gemstones, which are graded according to internationally recognized criteria (the so-called "4 Cs.").

Many years ago, Chinese pearl farmers began cultivating coreless freshwater cultured pearls in oysters that they farmed in the tributaries and canals of the Yangtse river system. Chinese freshwater pearls have an attractive, nearly spherical shape. The largest ones can be as much as 10 mm in diameter. The spectrum of colors ranges from white, rosé and green to intensive red and lilac hues. In the cultivation process, a bit of living tissue which forms mother-of-pearl is grafted into the body of the oyster so that these pearls have no core and consist entirely of nacre.

A "choker" is a collier that clings close to the neck, almost as though it were choking its wearer. A short, close-fitting chain made of links or a neck-hugging collier made of one or more strands of pearls can each be described as a "choker." All of the pearls in a pearl choker are identical in size.

CIBJO is the international professional confederation of the jewelry industry. Founded in 1926, the organization has been named "Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie, Perles et Pierres" since 1961. All major industrial nations are members. Among the CIBJO's most important tasks is to designate exact names and descriptions for precious stones and pearls. These official designations are listed in the so-called "Blue Book."

The citrine is a member of the quartz group. Synonyms are "gold topaz," "Madeira topaz" or "Spanish" topaz, although these citrines only superficially resemble genuine topaz because they share a similar color with that gem. The name "citrine" derives from the lemon-yellow color, although the most avidly coveted citrines are clear, luminous yellow to brownish-red. The citrine is a hard, non-fissile, and comparatively hard-wearing stone. Its primary sources are Brazil, Madagascar, and the USA.

Citrine is a rather rare stone in the quartz group. Citrines occur in a spectrum of colors ranging from pale or dark yellow to golden brown. Most of the citrines sold today have been colored by firing them together with amethyst or smoky quartz. This coloring method has been a common practice for more than 200 years. When citrines are heated to a temperature between 470 and 560 degrees Celsius, their color gradually changes to the desired yellow hue.

The term "clarity" (purity) is one of the four quality criteria (the "4 Cs") according to which the value of a diamond is appraised. Absolutely perfect diamonds, which are entirely free from inclusions, are rare exceptions. The purity of diamonds is judged very strictly and classified according to an internationally accepted evaluative system. The highest grade is "IF" ("internally flawless," i.e. entirely free from inclusions). The equivalent German term lupenrein means "pure under a loupe." The other grades are as follows. VVS1 to VVS2 means "very very small included" and refers to diamonds with miniscule inclusions that are invisible to the unaided eye.

Many gemstones can be split in one or more directions. The breakage occurs along perfectly flat planes. This attribute is called "cleavage" and depends upon the lattice structure of the crystal. Depending upon how easily a gemstone can be split, one can differentiate between perfect, good, and unclear cleavage. A gemstone that cannot be split at all has "no cleavage." The cleavage of a precious stone must be taken into account when cutting, polishing, and setting the stone because a slight blow or unduly strong pressure can all too frequently cause a gem to split.

A "collier de chien" is a close-fitting, broad or multi-strand necklace. It was the most popular piece of jewelry during the 1920s and it played an important role in the fashions of the late 15th and mid 18th centuries. Nowadays the collier de chien form is interpreted in many different ways. Colliers of this sort are also available with pearls, diamonds, or colored stones. The name comes from the French language and literally means "dog's collar."

The technical term "color" is one of the four quality criteria (the "4 Cs") according to which the value of a diamond is appraised. Stones are judged by comparison with color scales. The majority of these scales have 12 quality grades. The highest grade is "very fine white," which is used to describe diamonds that are absolutely colorless. Diamonds of this quality are identified by the letters "D" and "E" or by the term "river." "Fine white" diamonds are identified by the letters "F" and "G" or by the phrase "Top Wesselton." White stones are identified by the letter "H" or by the word "Wesselton." Most diamonds are delicately tinged with color, often with a slightly yellowish cast.

Color is used as a technical term to describe one of the four quality criteria (the "4 Cs") according to which the value of a diamond is appraised. Most color scales have twelve quality grades according to which diamonds are evaluated. The highest grade is called "very fine white" and is used for diamonds which are absolutely colorless. Stones of this sort are graded "D" and "E" or identified by the words "Top Wesselton." "Fine white" stones are graded "F" and "G" or identified by the word "Wesselton." Most diamonds, however, are not perfectly colorless; a yellowish tinge is most common. This yellowish cast is readily visible starting with stones graded "M" or "Top Cape."

The phrase "colored stone" is used for all precious stones except diamonds and agates. On the other hand, colorless precious stones are sometimes included in the category of "colored stones." The term "colored precious stone" is also frequently used to emphasize their preciousness.

Corals grow in the ocean at depths of 300 meters or less. Soft polyps very slowly build ramified structures by excreting a chalky substance from their disk-like feet. Coral is thus the scaffold of the polyps, which live in tiny indentations in the branches. Jewelry-quality coral, which primarily grows in the Mediterranean Sea and the Pacific Ocean, occurs in a wide variety of red and pink hues. Particularly desirable are the deep red variety, which experts call "oxblood" or "moro" coral, and a powdery pink variety known as "angel's skin."

Corundum is essentially colorless. If trace amounts of other elements (primarily iron and chrome) are present, corundum can display every color of the rainbow. Colorless corundum is a valuable gemstone. After centuries of confusion in the nomenclature, international convention has now agreed to use the word "ruby" to describe red corundum and to use the word "sapphire" to denominate corundum stones in all other colors. The word "corundum" derives from a language spoken on the Indian subcontinent, in which tongue a similar word meant "hard stone." This etymology is indeed appropriate because with a hardness of "9" on the Mohs' scale, corundum is the world's second-hardest gemstone, exceeded in hardness only by diamond. Corundums are found on every continent.

The Cullinan is the "Star of Africa." The largest raw diamond ever found was named after Sir Thomas Cullinan, the director of a South African mine where this diamond, which weighed 3,106 carats, was discovered in 1905. Nine important, large diamonds and 96 smaller stones were cut from this one raw diamond. The large diamonds bear consecutive numbers. The largest of the nine, Cullinan I, weighs 530 carats and is the world's largest cut diamond, a distinction which earned it the cognomen "Star of Africa." It ornaments the scepter of the Queen of England and is kept in the Tower of London.

The cultivation of pearls was first invented in Japan at the beginning of the 20th century. The original method is still in use today. A kernel, typically a spherule which has been lathe-turned from a seashell, is implanted into an oyster together with living mollusk-tissue that produces mother-of-pearl. The bivalves are then returned to the water and cleansed at regular intervals. Inside the shell, the implanted tissue continues to produce mother-of-pearl, gradually covering the kernel with layer after layer of mother-of-pearl. At least 18 months' time is required to produce a pearl in this manner. The resulting pearls are called "cultured pearls" or "cultivated pearls."

Cultured pearl is the English equivalent of the term that is most frequently used in Austria and Switzerland to describe cultivated pearls. Pearls are typically cultivated by inserting into a bivalve a kernel (usually a lathe-turned spherule made of natural mussel shell) together with a bit of living tissue that produces mother-of-pearl. The bivalve is returned to the water, where it is continually monitored and regularly cleansed. The implanted tissue continues to produce nacre, with which it covers the kernel. The bivalve requires at least 18 months to produce a cultured pearl.

The cut is the treatment given to the surface of a colored stone or diamond. A good cut can enable the gem to reveal its inherent beauty, color, and gleam. The lapidary art was probably first practiced in India. Prior to and into the 15th century, the treatment given to gemstones usually consisted solely of polishing their natural crystal or cleavage surfaces. Faceted cuts first became widely known during the course of the 15th century. Colored stones are polished by abrading them with polishing disks made of lead, bronze, copper, or tin. Diamonds can only be cut by other diamonds. The hardness of a diamond varies depending on the particularities of its crystal planes and its several axes. Many of the phases in the work of polishing and cutting colored stones and diamonds cannot be accomplished by machines and must be performed manually.

The term "cut" (polish) describes the most important of the four quality criteria (the "4 Cs") according to which the value of a diamond is appraised. The cut given to a diamond is of decisive importance in determining its value. Only a perfect cut can bring the diamond to life and allow it to fully display its fiery sparkle. A good cut reflects light from facet to facet, bundles incident light, and ultimately radiates it outwards again from the top of the stone. If the cut is imperfectly executed, light is lost. The highest brilliance is achieved only by a diamond on which all the facets are correctly proportioned and arranged.