[Jewelry making - Article 00170] - Re: [Orchid] Naming gem materials

[Peter W . Rowe]

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>     I can't imagine anyone on this list mistaking yellow jade for
>     "serpentine' which is as soft as butter (it's soapstone after all)
>     when compared to jade; why not just take out your trusty steel
>     pocket knife and try to scratch it? Only Corundum, beside jade
>     wouldn't scratch...good ole 'Moh'. I always 'narrow down' my
>     possibilities with the easiest protocol being done first. 

Captain,

    I hate to be blunt.  But attempting to identify any unknown gem via a
    scratch test is a really good way to find yourself buying something
    you didn't want to own, after you've damaged the hell out of it with
    a destructive test.There are better ways, that don't damage the
    merchandise.Hardness tests, while useful with rough uncut materials,
    should generally not be used with cut and finished stones. And you
    REALLY need to go back and check your mineralogy books. Serpentine
    may be soft (3-4 on the mohs scale), but it's not soapstone, (also
    known as talc, or steatite), nor is it as soft as soapstone (which is
    1, at the bottom of the scale, and can be scratched with a
    fingernail).Jadeite is often found in close association with
    serpentine, and some serpentine carvings are quite close in
    appearance to jade, and it's considered, despite being softer and
    more fragile than jade itself, quite tough enough for good carving
    material. Jadeite's hardness usually around 6.5, and nephrite is
    usually around 5.5 to 6, so indeed, most steel pen knives won't
    scratch it.  But some modern steels are harder than you'd expect,
    and given the state of knife making these days, I'd not suggest this
    is a reliable test.  plus, even with a stone harder than the knife,
    persistent or unlucky scratch testing can cause unfortunate damage
    via chipping. And, may I point out that while corundum indeed won't
    be scratched by your knife, at a hardness of 9 on the mohs scale,
    neither will any of the other MANY minerals out there that are 6 or
    harder, including a whole raft of quartz gems, agates, jaspers, and
    others that might easily be mistaken for or used in similar
    applications as jade.  In fact, it's probably safe to say your trusty
    pen knife won't be able to scratch the majority of gems in use today
    using a true scratch test method. Yet, I promise you that if you push
    hard enough with the sharp tip of your knife, in just the wrong place
    on that corundum, (as discovered by many a stone setting with a
    burnisher or graver), you can indeed cause a sort of scratch on the
    sapphire.  It's not that the tool is harder, just that the tool can
    transmit enough pressure to cause a series of small crush or bruise
    marks that look just like a scratch... 

Peter Rowe

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