Lapidaries use the word "table" to refer to the upper polished surface of a jewelry stone. This planar surface, which creates the impression of depth in the stone, is typically surrounded by numerous facets. In baguette-cut or emerald-cut gems, these facets are arranged like tiny steps. The brilliant and navette cuts have interlocking, triangular, or rhombic facets.

The Tahitian pearl is the dark variant of the South Seas pearl. Above all in French Polynesia, Tahitian pearls have been cultivated since the 1960s inside the black-lipped pearl-bearing bivalve Pinctada margaritifera. These pearls reach impressive sizes between 8 and 12 mm, and may occasionally even exceed 15 mm in diameter. Their rich luster gleams in shades of gray, silver, and black, and is sometimes covered with a breath of shimmering red, blue, or green. The most avidly sought hue is called "peacock," which has a dark greenish shimmer similar to the showy feathers of the bird for which it is named.

Jewelry began as functional objects: i.e. as amulets or talismans. In the past, people wore particular gemstones or symbols to protect themselves from evil or to attract good fortune. In the course of history, jewelry gradually lost much of its original symbolic function and was reduced to playing an exclusively ornamental role. Nonetheless, pieces of jewelry crafted in the shape of particular symbols often play more than merely an ornamental role. The heart, for example, is universally understood as an emblem of love. Cruciform jewelry is often worn as a protective amulet. The trend towards charm bracelets with their many little good luck charms is a "charming" expression of this preference.

Tanzanite is a relatively young beauty, but it isn't a new mineral. First discovered in 1967, tanzanite is a specially colored variety of zoisite and has thus far been found only in Tanzania. The stone's appeal derives from its usually immaculate transparency and intensive blue color, which can sometimes verge towards violet. Some tanzanites are bicolor and covered with a purplish tinge.

Taper refers to a necklace or bracelet whose volume decreases from the midpoint towards the clasp. A tapering pearl collier, for example, has its largest pearl situated at the midpoint. The diameter of the strung pearls decreases regularly as their distance from the midpoint increases and their nearness to the clasp increases.

The teardrop cut is a particularly charming type of cut. As its name states, teardrop-cut gems have been cut and polished into the shape of a droplet. The table too is shaped like a teardrop, and this shape is further emphasized by the design of the surrounding facets. The names "briolett," "poire" (French for "pear") and "pampel" are also used to describe stones which have been cut into teardrop shape.

The terrace cut is one of the facetted cuts. It has a rectangular shape. The rationale for the name becomes apparent when one views this cut from the side: the terraced shape has characteristic "steps" leading upwards to a flat top or "table." This cut has been further evolved to create the emerald cut, in which the four corners of the rectangle are blunted.

The value of a diamond is determined according to internationally recognized criteria (the so-called "4 Cs"). The most important criterion is the color, which is defined according to an internationally uniform color scale. This scale is usually subdivided into 12 gradations. The top of the scale is the highly fine white known as "river." The lowest end of the scale is reserved for the toned colors, which have a more or less intensive yellowish tone and which are known, for example, as "Cape." This yellowish tone is first readily visible in stones graded "Top Cape" and is further subdivided into various grades that are assigned letters from "M" to "Z."

No longer in widespread use, the phrase "Top Wesselton" describes a particular color of diamond. Second only to river, Top Wesselton is the second-highest grade of a diamond's color and describes a "fine white." In the CIBJO's international color scale, this level of quality is subdivided into "fine white +" and "fine white" and given the letters "F" and "G."

The name "topaz" was not uniformly applied in the past, when it was used to refer to all yellow, golden brown, and sometimes also green gems. Nowadays topaz is sometimes also called "precious topaz" and designates a group of gemstones whose members occur in many different colors. Most of the colors are pale or pastel, and their hues range from yellow to blue and from green to red and violet. The most valuable topazes have colors ranging from pink to reddish orange. Topaz most commonly occurs as a yellow stone, which sometimes causes it to be mistaken for citrine. Topaz, however, is harder and more refractive than citrine. The only weakness in topaz is its easy cleavage. Brazil is the most important source of topaz.

The tourmaline group includes stones which occur in a wide variety of colors. Some color variants have names of their own, e.g. tourmalines whose colors range from pink to red are known as "rubellite." Black tourmalines are also known as "schörl." Green ones are termed "verdelite." Blue tourmalines are called "indigolite." Monochrome tourmalines are quite rare. It is much more common for a tourmaline to exhibit different shades or sometimes even entirely different colors, hence the name: turmali is the Singhalese word for "stone with a mixture of colors." Brazil is the world's most important source of tourmaline.

Transparency refers to the degree to which a gem allows light to pass through it. A gem can be transparent, translucent, or opaque. Transparency is an important factor in determining the value of a gem. Inclusions or cracks detract from a stone's transparency, which is subdivided into several degrees. Specialists describe a gem as "transparent" when incident light is reflected unhindered, as "moderately transparent" when light is reflected with less intensity, and as "opaque" when light is completely absorbed.

The original, natural colors of many precious stones can be altered artificially. Irregular or unattractive nuances of color can be improved by heating the gems to a temperature of several hundred degrees Celsius. The best-known treatment is the thermal processing of amethyst: depending on the duration and temperature of the heat treatment, an amethyst's color can be changed to yellow (citrine) or green (prasiolite). So-called "firing" can give a sea-blue color to aquamarines which have a naturally greenish tinge and can brighten the hue of originally dark tourmalines. These alterations in color do not look at all artificial and do not harm the gems.

The trilliant is a cut that gives a diamond the shape of a symmetrical triangle. Diamonds cut in this shape are often set alongside colored stones or large diamonds. The "troidia" cut is another triangular cut with three convex sides and, depending on the size of the gem, from 77 to 107 facets.

No other mineral has been revered as a holy stone and talisman by so many cultures around the world. Mankind has perennially been fascinated by turquoise and its opaque, sky-blue to apple-green color. The name, which means "Turkish stone," recalls the days when turquoise reached Europe along trade routes that passed through Turkey. The most avidly sought color, a clear sky blue, is also the rarest hue. Most turquoises have dark veins of other minerals running through them. The best-quality turquoise comes from Iran. This mineral isn't especially hard and is slightly porous. The latter attribute makes it sensitive to perspiration, cosmetics, and perfume.