Tuesday, 18 June 2013

Introduction to Green tourmaline

Green tourmalineThis color variety of tourmaline has no separate name; it is as well-known as rubellite and indicolite. 

Appearance

Green-colored tourmaline comes in a mire range of different shades, so, at first sight, many greet tourmalines may look very similar to other gems. Shaw may include the yellowish-green of some olivine, or the stronger, deeper green of others; a lights paint box grey, like some zircons, is also possible as is a stronger vets& of this color, like some African emeralds. Tourmaline cr be a brilliant green, a touch colder than the color Omer aid (this is typical of tourmaline); or leaf green, tending h deep olive green (also very typical and known, in fact, a tourmaline green). If they are large, green tourmalines are given either a step cut (not always with truncated cornet) or a pear-shaped or oval mixed cut. If the stones are small they are most often given a round or roundish oval. Mid to light-colored specimens have good luster. Clarke stones often look a bit opaque. Many are virtually heel inclusions.

Distinctive features

RubelliteThe more definite or darker shade is characteristic. Loss of transparency along the stone particularly in gems that are cut rectangular is peculiar to tourmaline. Mid-green stones that are given a rectangular cut often show alternate longitudinal lines of lighter are darker color because of the way in which light is reflecti4 from the pavilion facets. This optical effect is unique and. therefore distinctive. But when the color is similar to that at other gems, the identity of the stones can only be distil-gushed by measurement of physical characteristics suth as density and refractive indices.

Occurrence

Green Tourmaline
Green tourmaline is found in Brazil, Its United States (Maine), Tanzania, Mozambique, and Namibia It is also extracted in the Soviet Union and from the gem gravels of Sri Lanka, where the lighter stones, some-what like olivine, are the most common. It is quite plentihr and widespread.

Value

As with rubellite and indicolite; only the lively mid-colored stones are valuable When the color is min) characteristic pale green, or the most typical dark or olive green they are worth much less.

Simulants and synthetics

It is neither imitated nor produced synthetically.

Writer – Curzio Cipriani and Alessandro Borelli

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