[Jewelry making - Article 00334] - Re: [Orchid] Stone Setting - getting rid of graver's marks

[Bruce Holmgrain]

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>         I have never damaged a solid agate or jasper cab with a
>     file....the rounded surface is the key here folks! 

    I suspect that the cryptocrystaline nature of the chalcedonies plays
    a part here. The interlocking of the crystals make for a tougher
    stone than ... say amethyst or citrine (same mineral). I rarely work
    with those stones. My work habits have needed to accomodate some
    more delicate stones that scratching or chipping might in the end
    prove fatal. 

>         Re breaking a diamond....Don't kid yourself.  A diamond
>     doesn't even need a brass hammer to be broken.  Simple hand
>     pressure on a thin area such as around the girdle or even proper
>     alignment to the grain can break one. 

    In fact, I broke a .01-.02 recently with my thumbnail. Another
    first. 

>         We are talking cleavage and toughness here, not hardness. But I
>     don't believe any of us when setting a stone, purposely pushes the
>     point of a tool into a surface nor are we purposely careless when
>     setting diamonds or other hard stones. 

    My point was that when burnishing the inside edge of a bezel, it is
    nearly impossible to not touch the stone and my personal experience
    has been that this practice will damage the stone from time to time.
    It has happened to me with corundum and several softer stones. Thus
    I learned to use a bronze burnisher in this situation. I can't
    remember ever damaging a stone with bronze. 

>         What I was suggesting was that knowing the relative hardness
>     of your tools and stones being set, can certainly save a setter (or
>     anyone doing the process) a lot of heart burn. And, there are some
>     things one can get away with if they understand the differences.
>     That doesn't mean we can grab a file and saw away at a stone...any
>     stone. 

    It left some of us with the impression that you thought that it was
    good form to finish all bezels and prongs with a file. Especially
    with any stones having a hardness of 6 1/2 +. If that was not what
    was intended, I apologize for not reading so well. 

>         By the way, do you know that many of the wheels used to smooth
>     metal contain SiC?  Some are looked upon as b eing 'pumice' wheels
>     (containing simple pumice powder which is a soft volcanic stone)
>     but are actually made with SiC which is a 9.5 hardness.  

    Around here, rubberized abrasive wheels with silicon carbide are
    labeled such. I can't imagine why someone would think that SiC
    wheels would contain pumice. Pumice wheels are labeled pumice. My
    experience has shown that pumice wheels can be used safely to finish
    prongs and bezels on stones as soft as strontiun titanate {6 on the
    Mohs scale). 

Bruce

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