[Jewelry making - Article 00060] - Re: [Orchid] Holly Blue Agate Vs Chalcedony?

[Lee Einer]

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>     Technically, not a thing, Noel. Holly blue agate IS chalcedony.
>     Sard, sardonyx, chrysoprase, agate, jasper, chrysocolla,
>     bloodstone and myriad others (such as flint) are also varieties of
>     chalcedony. Basically, chalcedony is a cryptocrystalline (invisible
>     to the eye) form of quartz. The differences among the different
>     varieties are in the other trace. 

    Agreed with the notable exception of chrysocolla, which is a copper
    mineral. I am very happy when chrysocolla is well-infiltrated with
    silica, as this makes it cuttable- chrysocolla which is not
    well-silicated is soft, crumbly and so porous it will hiss when
    wetted. 

    Of course, there is that lovely stuff which is known variously as
    "chryocolla gel" or "gem chrysocolla" which is really so much silica
    and so little chrysocolla that it could probably be referred to as
    "chrysocolla-colored chalcedony." 

Lee
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