White Topaz: What Is It?

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Topaz is a mineral that at gem-quality level is used mainly for earrings and necklaces. Even though when found in nature the greatest amount of the mineral is without color, there are other colors made from this “white” clear topaz. As a crystal without color, the assessment of the white topaz is lower in value than colored topaz. But heating and treating of the white crystal produces alternative colors.

Composition

All topaz is a hydrous aluminum silicate (water, the element aluminum and silicate, which consists of the elements silicon and oxygen). Topaz is a neosilicate (a structural type of silicate) with the chemical formula of AL2[(f,OH)2|SiO4. It is commonly found in felsic igneous rocks, which are light-colored igneous rocks containing feldspars and quartz, and some crevices in the earth’s crust where hot mineral water has deposited minerals, called hydrothermal veins, as well as in the hydrothermally changed rocks surrounding them. On rare occasions topaz can be found in metamorphic rocks like quartzite and schist.

Features

White topaz, like all topaz ,has a vitreous luster, distinct pleochroism (displaying different colors when viewed at different angles), a hardness of 8 on the Moh’s Scale, perfect basal cleavage, a refractive index of 1.610 to 1.638, a specific gravity ranging from 3.4 to 3.6, and it belongs to the orthorhombic crystal system, which is a crystal system with three axis. Each axis is a different length and all cross each other at right angles.

Cleavage refers to when a crystal splits, depending on the crystal lattice, on the natural planes of weakness. Topaz’s type of cleavage is called basal cleavage, meaning its points of weakness break parallel to its base. Due to this topaz can form internal flaws and chip when hit hard enough, so jewelers need special practice to cut topaz. This makes topaz more suited for jewelry less likely to come into contact with anything.

Function

Despite its potential breaking, white topaz is used as a diamond substitute in jewelry, usually in the brilliant cut. However, it displays less color and brilliance than diamond.

Other Colors

White topaz is often used in heat and radiation treatments to form blue topaz. White topaz is also treated vapor veneers to produce different colors, such as a titanium dioxide vapor coating to make “mystic topaz.” In the gem business, white topaz also goes by the names silver topaz, clear topaz and colorless topaz.

Deposits

Topaz deposits are situated around the world, including Africa, Pakistan, Burma, Australia, Tasmania, Brazil, the United States, Mexico, Sri Lanka and Japan.

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