All, I was very surprise to read that Lord of the Rings did not put
mute faith into what he observed with his eyes in a stone. In my
experience 99% of all people involved in stones use visual
observation as their determination of the identification of a stone.
Instruments measure properties of a gemstone that can not be
changed by a knowledgeable cutter. In the case of a doubly
refractive stone an instrument that measures the unique electrical
conductivity of each stone is a more reliable indicator of the
identity of the stone. I can cut a doubly refractive gemstone to
minimize the amount of double refraction you will see through a
gemscope. I often do this with zircon. An experienced cutter knows
that the one way we can optimize the color and attractiveness of a
gemstone is to manipulate the stone so that the visual appearance of
the stone is optimized. What this means is that in the cutting of a
gemstone I can manipulate the color and amount of clarity you see
when you hold a stone. Any visual effect I can manipulate. The
last thing I rely upon when I am identifying a gemstone is visual
clues. Measurements of refraction, specific gravity, and electrical
conductivity are much more decisive than visual identification.
Gerry Galarneau