[Jewelry making - Article 00030] - Re: [Orchid] Brittle Carnelian

[Terry Ogden]

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Harry

>     It sounds like I will just have to cut slow if I want the pretty
>     color. OK. 

    Don't know if you mean cut as in grind or cut as in slice. Grinding
    is slower and there was a post to your subject that I totally
    neglected to mention, and that is the course grind does damage the
    stone. There is a formula for this and I forget what it is, but the
    rule of thumb that I distilled it down to from what I remember is,
    leave 3 times the depth of the grit to be removed for the next
    process. This only applies as I have seen, to below about 150, 400
    and up does not leave appreciable damage, but it must be accounted
    for or you will over grind to get a good finish. If you are making
    the stone, and then the mount to fit, no problem, if you are making a
    stone to fit a piece, it then you have to follow this rule or you
    will be always under, or poorly finished. In cutting, sometimes
    slower is good, sometimes it is bad for the blade. I vary the
    pressure on the blade to minimize glazing of the blade surface. I
    have read 5lbs of weight is about right, but for me 1.5 to 3.5 lbs
    seem to get the best blade life and cut quality. I have had where I
    was getting a lot of glazing, and increased my weight by 1/2 lb and
    the glazing stopped and my cut speed went up. 

>     At shows I've always seen lots of carnelians that were a set of
>     cracks held together by a bright color. It made me wonder if they
>     were over- heated, cooled too quickly or otherwise improperly
>     treated. 

    Both will do it, I start from a cold oven add the stone, and cool
    down is slow, it will be a day after heating before the stone is
    removed. I wait until I can touch it by hand. I have not had that
    type of cracking in any of my stones. 

>     Does this produce usable drusy? I don't live near any source of
>     carnelian, but I guess I could purchase some untreated material and
>     try this. 

    Yes, and it will have a very unique look. I have material that is
    red on the base, very like the color of ruby and gradually changes to
    clear at the tips, I also have some that is lavender at the base and
    changes to orange at the tips unfortunately I had not started my
    notebook at the time and do not have a record of conditions or of the
    stone before heating. A good inexpensive stone to try this with would
    be Brazilian Agate. It will have a red to orange rind that is very
    shallow in depth, and ugly in the middle. Heating this stone does
    very nicely, and I would recommend it to learn heating with. To try
    for the drusy, get the larger stones, they seem more likely to have
    usable pockets, large orange size to grapefruit. As they will pop
    when you find one, I put a grate or some kind of restraint over it, I
    have not lost a heating element, but I felt it was only a matter of
    time before I did. 

Good luck.
Terry
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