Transparency


The transparency of a gem depends on the quality and quality of light that is transmitted (allow to pass through) by it.

  1. Quality of Transmitted Light

    The quality of light transmitted by a gem depends on the "obstacles", such, as minute imperfections or peculiar structure, that it encounters during its passage through the stone. If light were allowed to pass through a gem without any distortion or distortion, it would be classed as perfectly transparent. Actually, of course, no substance is COMPLETELY transparent.

  2. Quantity of Transmitted Light

    Light may pass through a substance with no appreciable distortion, yet it may, because it absorbs much of the light, be classed as not completely transparent. The amount of absorption varies from a very small percent absorbed in transparent stones, such as diamond and rock crystal, to almost complete absorption by black chalcedony. A strongly colored gem such as a dark-red garnet absorbs much light therefore, it does not exhibit maximum transparency.

The degree of transparency of a gemstones is described by the following terms:

  1. Transparent

    Gems through which light passes with no appreciable distortion and/or absorption are said to be transparent. Images can be seen clearly through transparent stones. Examples are the finest qualities of diamond, ruby, emerald and rock crystal.

  2. Semitransparent

    Those gems that show a small amount of absorption and/or distortion of transmitted light are classed as semitransparent. Images can be seen through semitransparent gems, but they are not as clear and sharp as those seen through transparent stones. Examples are some varieties of amber and the finer specimens of jade.

  3. Translucent

    In order to be classed as translucent, a stone must show a certain amount of distortion and/or absorption of light, but it will pass a large quantity of the light that enters it. A good example is precious moonstone.

  4. Semi-translucent

    Gems classed as semi-translucent suffer a large amount of both absorption and distortion; therefore, they pass very little light. As a rule, light penetrates only through thin sections of these stones. Examples are obsidian and amazonite.

  5. Opaque

    When cut as gems, many minerals, such as black chalcedony and lapis-lazuli, are opaque, since in thicker pieces they transmit no light. In the strictest sense of the word, only those substance that show metallic luster can be classed as opaque, since any other substance, if cut sufficiently thin, will show some transmission of light. Examples of metallic opaque minerals are pyrite and marcasite.


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