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  2. Interference colour chart - Wikipedia

    en.wikipedia.org/wiki/Interference_colour_chart

    With a known thickness of the thin section, minerals have specific and predictable colours in cross-polarized light, and this chart can help identify minerals. The colours are produced by the difference in speed in the fast and slow rays, also known as birefringence.

  3. Category:Quaternary colors - Wikipedia

    en.wikipedia.org/wiki/Category:Quaternary_colors

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  4. List of mineral tests - Wikipedia

    en.wikipedia.org/wiki/List_of_mineral_tests

    Mineral tests are simple physical and chemical methods of testing samples, which can help to identify the mineral type. [1] This approach is used widely in mineralogy, ore geology and general geological mapping. [2]

  5. Ametrine - Wikipedia

    en.wikipedia.org/wiki/Ametrine

    Ametrine, also known as trystine, golden amethyst, or by the trade name bolivianite, is a variety of quartz with alternating zones of purple and yellow-orange coloration. Its name is a portmanteau of amethyst and citrine. While ametrine is commonly referred to as a combination of these two quartz varieties, some sources claim this is not ...

  6. Glass coloring and color marking - Wikipedia

    en.wikipedia.org/wiki/Glass_coloring_and_color...

    In borosilicate glasses rich in boron, sulfur imparts a blue color. With calcium it yields a deep yellow color. [4] Manganese can be added in small amounts to remove the green tint given by iron, or in higher concentrations to give glass an amethyst color. Manganese is one of the oldest glass additives, and purple manganese glass was used since ...

  7. Pleochroism - Wikipedia

    en.wikipedia.org/wiki/Pleochroism

    Pleochroism is an extremely useful tool in mineralogy and gemology for mineral and gem identification, since the number of colors visible from different angles can identify the possible crystalline structure of a gemstone or mineral and therefore help to classify it. Minerals that are otherwise very similar often have very different pleochroic ...

  8. Amethyst (color) - Wikipedia

    en.wikipedia.org/?title=Amethyst_(color)&redirect=no

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  9. Gemstone irradiation - Wikipedia

    en.wikipedia.org/wiki/Gemstone_irradiation

    Gemstone irradiation is a process in which a gemstone is exposed to artificial radiation in order to enhance its optical properties.High levels of ionizing radiation can change the atomic structure of the gemstone's crystal lattice, which in turn alters the optical properties within it. [1]