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Posted in response to Re: Ok Faceters from Ward on December 07, 2007 at 07:54:23:

Re: Re: Ok Faceters

Hi again Ward,

Without being able to inspect the particular piece of rough first hand it is difficult to give advice regarding it.

Regarding the play of color flashes the orientation considerations for your Siberian amethyst primarily concern any color zoning in your rough, not crystallographic orientation.

If your rough is highly color zoned, you may be able to discern areas in it that are more reddish and others that are more blueish. If you place one or other of the colored zones predominately in the culet area, the effect of that will tend to make that color flash more predominate in the stone. If your stone is highly zoned with differentiated colors, orienting the stone so that the pavilion contains a mix of both colors will help produce a broader display of color in dispersive flashes.

I have personally tended to steer away from highly saturated amethyst and other materials because I like to cut large stones. You haven't mentioned the size of your rough or the shape of the stone you are contemplating cutting from it. A good deal of the Siberian I have inspected is so dark I passed on it, preferring amethyst of more medium range saturation for larger stones.

If your rough is very dark, you might actually want to consider orienting it so as to place any lighter zoning in the culet area. There are a lot of variables at play here, so it is difficult to give general advice.

You have also not mentioned having any particular design in mind for the cut. One thing I will mention in the way of general advice is my experience has been that designs with low, hubcap profile type crowns will help maximize the brightness, but higher crowns seem to be generally preferable for fostering dispersive displays.

I am growing increasing fond of checkerboard style crowns for lower RI materials like quartz. If your rough is very deeply saturated, you may want to consider a design which has the pavilion mains cut close to the critical angle and a medium to moderately high checkerboard crown. The play of red and blue flashes from Siberian amethyst cut that way can be quite impressive.

Keep on Rock'n!

From Bob Keller - December 07, 2007 at 11:49:29

Message: 65645

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