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If these color effects (pleochroic effects)
aren't properly compensated for in gemstones where they exist,
the result can often be disasterous, reducing the value of
a gem to a small fraction of what it would have been if oriented
properly. In the case of our apatite, however, we have nothing
to worry about.
Another important consideration for proper orientation
of most gemstones is the impact of inclusions. Many rough
materials have inclusions, and while it may not always be
possible to avoid having flaws in a finished gem, a good gem
cutter will orient the stone to minimize the visual impact
of the inclusion. In our case, the apatite is fairly "clean,"
with only minor imperfections near the surface, which should
cut out. So, orienting in this particular case is fairly straightforward:
we'll place the table parallel to the long, straight edge
of the crystal and will use the roughly rectangular crystal
shape to our advantage to obtain the largest stone possible.
Next, we'll grind small portions of the rough
away to better approximate the shape of the finished gem.
This is called preforming and is usually
(but not always) done. Some crystals are so well shaped to
begin with that no preforming is necessary. in the case of
our apatite, there are a few jagged, angular parts on each
end of the crystal that we need to take care of, and we need
to grind a flat spot where the table will go. We will also
use this opportunity to grind away any major imperfections
near the surface.
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