[Jewelry making - Article 00149] - Re: [Orchid] Agatized dinosaur bones

[leonid surpin]

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    From the outset I will concede the point that for practical
    applications, the distinction is without a difference, but since I am
    a gemology geek, I would like to correct the following: 

    Chalcedony nomenclature is colloquial and not scientific. 

    There are 2 versions of origin of "Chalcedony" 

    First is ascribed to Georgius Agricola ( Georg Bauer ), who named it
    after town of Calchedon near Istanbul. Second is that name was made
    after Greek translation of Carthago (Carchedon), which was a seaport
    used to transport it. 

    Jasper (any opaque agate-like chalcedony) 

    Jasper is metamorphic rock composed of Chalcedony, Opal, and
    different admixtures. 

    Chalcedony (Any agate like material that is white, blue or gray). 

    Chalcedony is quartz which formed with cryptocrystalline structure.
    There are several varieties of Chalcedony. Agate is one of them. 

    ( Yes, I am aware that GIA nomenclature includes microcrystalline
    quartz under Chalcedony. On that point I am in disagreement with my
    alma mater. ) 

>     Agate (Any transparent or translucent chalcedony not called
>     Chalcedony) 

    It may be O.K. to think that from a lapidary point view, or may be
    not. As far as Gemology is concern, the definition is a bit loose and
    backwards. 

Leonid Surpin.
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