[Jewelry making - Article 00341] - Re: [Orchid] Naming gem materials

[Peter W . Rowe]

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>        Hi Peter, Well here you weren't so "startling" and have made a
>     few very good points, but firstly, you still confuse apples with
>     oranges: 

    Maybe I'm mixing up your fruits, but I was replying to the rather
    blanket statements you made, which might have been in reply to
    discussions of bead materials, but which did not limit themselves
    thusly in your replies. 

    Your post, to which this is a reply, is somewhat scrambled in terms
    of what seems to be my quoted statements, and what seems your reply,
    as much of what is unquoted is what I wrote, while many of your reply
    comments are in the quoted sections.  So I've somewhat selectively
    edited your post for this reply, to isolate your comments, which I'll
    address. 

>         Sure, "anything" is possible but with care, one CANNOT
>     'scratch' ruby or sapphire-an unexpected fracture inside, or
>     inclusion, could cause trouble but a good look at the piece in
>     advance precluses that happening  AND, you keep referring to set
>     (and obviously gem-grade) stones when this discussion was ONLY
>     about cheap bead minerals. Also, I've broken diamonds too-but not
>     scratched them 

    True enough.  My statement was that relying on a hardness test can
    be unreliable, especially for a beginner, since I assure you, it does
    NOT require an internal flaw in that ruby, for a graver or burnisher
    to leave what looks, even under a microscope, much like a scratch. 
    Technically, of course, it is a series of crushed or bruised areas,
    rather than a true scratch, and does not mean the tool is harder. 
    Just tougher.  But as I said, ask any setter whether he or she can
    seriously damage a ruby or sapphire, even a flawless one or a
    perfectly clean cheap flame fusion one, with careless bezel setting.
     The damage really will look like a scratch, not a series of chips or
    anything.  Any neophytes looking at that, could well assume that it's
    a scratch, and wonder if their tool is harder than the stone.  The
    reason it happens, of course, is that though the stone is much harder
    than the steel, it's also rigid and somewhat brittle, while the steel
    is much tougher.  The stone may blunt and deform the tool tip, but the
    tool tip can still exert pressure needed to cause the damage. 

    This difference between hardness and toughness is part of what makes
    hardness testing problematic.  True scratch testing requires a rather
    gentle deft touch. 

>>        So didn't you say jade would resist that scratch? Jade, both
>>     nephrite and Jadeite, are both SOFTER than quartz. But they are
>>     tougher. You might have to press harder... if your steel will
>>     actually scratch the quartz, then the same steel will surely
>>     scratch jade. 

>       Quite incorrect sir: jade, both nephrite and jadeite are tougher
>     AND harder-the best Samurai steel will not scratch any genuine jade
>     and will ALWAYS scratch quartz 

    A fully hardened high carbon steel can indeed be harder than 7 on
    the mohs scale, though only barely.  So a file, or the like, can
    sometimes with difficulty, scratch quartz.  Most knife blades are not
    hardened quite this much, with about 5.5 to 6 being average,
    according to charts published by Sinkankas, and others. 

    Nephrite, generally is generally listed as varying from 6 to 6.5,
    while jadeite is listed as 6.5 in Sinkankas's charts, and others.
    Individual specimens will very of course, and these may be close
    enough that given the much higher toughness of jade, can make
    comparing them with quartz difficult. Nevertheless, quartz is harder
    than jade in terms of just it's formal hardness specification.  The
    actual ease with which you can scratch it varies a lot according to
    technique.  But just try GENTLY drawing the point of a quartz crystal
    across any piece of jade you wish.  You'll find you can leave a
    scratch on the jade, while drawing a sharp corner of the jade across
    the quartz crystal will not do the same.  And just for fun, I just
    took a nice jadeite cab I've got, which already needs recutting due
    to a chip, and tried to scratch it with my old victorinox swiss army
    knife blade.  Not samurai, of course, but rather more typical of what
    most knife wielders will have around.  It leaves no mark on the jade,
    nor did it do a thing to a Brazilian agate cab.  Turned over, and
    tried again on the unpolished undersides, both stones received a
    mark of steel rubbed off, just as gold would do on a touchstone,
    while neither stone itself was scratched. 

    So much for "ALWAYS:".  but of course, you did specify Samurai steel
    this time...  Want to send me some to try?  Not being a ninja
    lapidary, I don't happen to have that around to compare... 

>        And never did I say that it was a "good......" proof, only that
>     CHEAP stones can easily be ID'd with sharp steel. 

    OK.  If that was stated in a post earlier than the one I replied to,
    I wasn't aware of it.  Of course, the truth of this depends, still,
    on just which cheap stone one is talking about.  You can get junk
    jadeite that is inexpensive and cheap because the color is crappy, but
    it can still be jadeite.  Certainly, even a soft metal tool will
    easily damage those jade substitutes that are calcite or the like. 
    no argument there.  Those are the ones that "fizz"... 

>       Yes, yes , but we're still merely discussing hardness testing-why
>     keep inserting additional factors. I often DO just 'smell' an
>     emerald, probably using some of your suggested acquired skills, but
>     I stll buy and sell jade regularly and, if in doubt, ALWAYS use the
>     scratch test-I'm usually in a jungle or mountain somewhere and WILL
>     alwaYS have my 'sophisticated' trusty 'moh/testing' equipment
>     along, call it a knife or whatever you will... 

    I mentioned other tests because you said I suggested that one needed
    to pay big bucks to have those tests done.  My point here was that it
    need not be that complex, and one even with visual observation, was
    already considering far more than hardness. 

    I do not dispute, at all, your ability to reliably determine jade in
    the field. I can do it too, and I too, might sometimes check hardness
    on rough materials if I needed to.  But your statement, without other
    qualifications, was that it was always all you ever needed,  a
    suggestion that will have the retail buyers without other knowledge
    or experience trying to test everything green and jade like with their
    pocket knives, just as some of those same folks still insist that if
    that white cut stone scratches glass, it must be diamond (an old
    wives tale that even today is responsible for damage to any number of
    costly showcase glass tops, when customers surreptitiously scrape the
    diamond they're being shown across the showcase, just to be sure,
    unaware that a CZ might also scratch the glass, and a moissonite or
    white sapphire surely would.  

    Had your posting, to which I replied, been worded even slightly
    differently, to suggest that all you USUALLY needed, was your
    hardness test, coupled with your experience,  I'd not have had any
    objections.   Try to remember that this list is read not just by the
    professionals, but by hobbyists and retail enthusiasts as well, who
    often will not have the experience to intelligently interpret a
    hardness test, or know when the results of such an attempt are
    meaningful. 

    By the way, I did enjoy checking your web pages.  Some nice work,
    sir.  Thanks for sharing it with us. 

Peter Rowe

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