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Green sapphire
This is the name given to the relatively uncommon,
green variety of corundum. In the nineteenth century it was
also known as oriental emerald, just as violet and yellow
corundum were called oriental amethyst and oriental topaz.
These names stemmed from a scant knowledge of mineralogy among
gem merchants and have now been abandoned.
Appearance Due to its iron
content, green sapphire is generally quite a strong, bright
green color, sometimes with green to bluish green or yellowish
green pleochroism. Individual stones are sometimes cut at
different angles from the rough crystal, to bring out the
best color. The luster is very good, as with all corundum.
The mixed, oval cut is the most common, but square or rectangular
step cuts are also used. These gems are usually small to mediumsized
and rarely exceed a few carats.
Distinctive features The color
is quite distinctive, especially combined with the particular
luster of corundum. While green tourmaline can, at first glance,
look fairly similar in color, it has more pronounced pleochroism,
the direction corresponding to the bluer green often seeming
rather opaque, and it is always, or nearly always, given a
rectangular, step cut strictly aligned to the elongated shape
of the prism. Green zircon can be quite similar to green sapphire
in both color and luster, but it has far less obvious pleochroism
and sometimes much stronger birefringence, easily detectable
with a lens. Many green zircons, however, have weak or virtually
nonexistent birefringence. In such cases, their density is
also very similar to that of corundum, so the physical characteristics
will need careful checking to establish a distinction.
Occurrence Green sapphire comes
mainly from Australia, but it is also found in the United
States (Montana) and Thailand.
Value As for all forms of corundum
except ruby and sapphire, its value is quite low. It is perhaps
worth a bit more than yellow sapphire, due to its greater
rarity and the difficulty of finding stones of any size.
Simulants and synthetics Not
being widely known or appreciated, this stone is not often
imitated. But green synthetic corundum has occasionally been
produced; it is of a brighter color than the natural mineral.
Bluish green synthetic spinel has also been produced, whether
to imitate green sapphire or zircon if is hard to say, as
it bears little resemblance to either.
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