[Jewelry making - Article 00619] - [Orchid] Serpentine, Jade, and Olivine

[Andrew Werby]

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Continue from:
New Colors in Jade?
http://www.ganoksin.com/orchid/archive/200503/msg00474.htm

>     Serpentine is indeed olivine, and good olivine/serpentine can be
>     translucent and have a 'ring' like jade but is much softer.  It
>     can be scratched with a pocket knife and even carved with good
>     files, yet it can also take a good polish using tin oxide on
>     leather at about 600rpm.  There is a deposit just on the edge of
>     Nelson city that used to be quarried and crushed for use on
>     agricultural land deficient in magnesium, and used to be used in
>     road making too. 

    I don't think so, John. There is a high-grade rather hard variety of
    serpentine called bowenite, that is translucent and makes a pretty
    good substitute for jade, but it's not as hard as olivine; it tops
    out at 5.5 on the mohs scale (which is harder than most knives,
    although files are harder). See

    http://www.emporia.edu/earthsci/amber/go340/gb4.htm  

    In its crystal form, olivine is known to jewelers as peridot, which
    is 6.5 to 7 on the mohs scale - a knife won't scratch it. It makes a
    nice clear green gemstone, and is hard enough to facet and set in a
    ring. Jade (nephrite and the harder jadite) falls in between these
    two in hardness. For more info on olivine/peridot see 

    http://ist-socrates.berkeley.edu/~eps2/wisc/oLect14.html  

    Olivine sand is hard enough to be commonly used for abrasive
    blasting; most serpentine is quite soft; this depends on the
    proportion of its two basic constituents. 

Andrew Werby
www.unitedartworks.com

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