The relative rarity of peridot and the ease with which it can be
simulated in glass, whose luster it approximates, probably account for
the low popular demand for this gemstone. Although peridot has little
brilliance and no fire, its unusual color and glassy luster produce a
unique effect that serves to make it attractive.
The color of peridot is an unusual bottle green that shades, in some
stones, toward yellow-green and, more rarely, toward brown. In 1952 it
was discovered that almost all of the brown gems believed to have been
peridot in various gem collections were actually of an entirely
unrelated species, which since has been named sinhalite. Brown peridot
still remains rare and is somewhat of a collector’s item.
[Illustration: To exhibit its unique color to best advantage,
peridot usually is cut so as to have a relatively large table, as
shown in these examples. The largest gem, weighing 310 carats, is
from the Egyptian island of Zebirget in the Red Sea and is the
largest cut peridot known. The other two, weighing 287 carats and
109 carats, are from Burma. (Three-fifths actual size.)]
The green of peridot, which is quite different from the green of other
gemstones, is due to some iron included in its composition. It is
suspected that a trace of nickel contributes to the liveliness of the
color.
[Illustration: This photo shows the color of peridot projected onto
the background. The larger gem is the 310-carat stone shown in the
prior illustration. The stone on the right weighs 109 carats and is
from Burma; the other peridot weighs 46 carats and is from Egypt.
(Almost actual size.)]
Peridot has a hardness of only 6½ and a rather strong tendency to
cleave, and these characteristics reduce its value for use in jewelry
exposed to rough wear. It is better used in pins, earrings, and pendants
than in rings.
Peridot is a gem name for the common mineral olivine, a magnesium
silicate. Olivine is fund in numerous places, and small gemmy pieces are
found in many localities. Many of the largest and best gems of peridot
have come from mines on the Egyptian island of Zebirget (Island of St.
John) in the Red Sea, but most gem peridot now comes from Burma. Great
numbers of small stones have been cut from olivine found in Arizona
gravels.
Centuries ago, peridot was known by the name topaz, since the stones
came from Topazos, the island now known as Zebirget. The name topaz, as
we have seen, is used today for an entirely different mineral species.