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  2. Tourmaline - Wikipedia

    en.wikipedia.org/wiki/Tourmaline

    Some tourmaline gems, especially pink to red colored stones, are altered by heat treatment to improve their color. Overly dark red stones can be lightened by careful heat treatment. The pink color in manganese-containing near-colorless to pale pink stones can be greatly increased by irradiation with gamma-rays or electron beams.

  3. Elbaite - Wikipedia

    en.wikipedia.org/wiki/Elbaite

    As a gemstone, elbaite is a desirable member of the tourmaline group because of the variety and depth of its colours and quality of the crystals. Originally discovered on the island of Elba , Italy in 1913, it has since been found in many parts of the world.

  4. Rubellite - Wikipedia

    en.wikipedia.org/wiki/Rubellite

    Rubellite is the red or pink variety of tourmaline and is a member of elbaite. Rubellite is also the rarest gem in its family. [2] It is occasionally mistaken for ruby. [3] These gems typically contain inclusions. [4] Notable countries where rubellite can be mined include Afghanistan, Brazil, Madagascar, Myanmar, Nigeria, Russia, and the United ...

  5. List of gemstones by species - Wikipedia

    en.wikipedia.org/wiki/List_of_gemstones_by_species

    This is a list of gemstones, organized by species and types. ... Tourmaline subgroup: Achroite (var.) Chrome (var.) ... Printable version; In other projects

  6. Chelsea filter - Wikipedia

    en.wikipedia.org/wiki/Chelsea_filter

    The "chelsea" filter was originally devised by Anderson and Payne in 1934 of the Gem testing Laboratory of the London Chamber of Commerce & Industry.The filter was devised with the collaboration of gemmology students of the Chelsea College of Science and Technology where Basil Anderson was an instructor for the Gemmological Association of Great Britain.

  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 ...

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