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Postage stamps dedicated to Peridot and Olivine!
image location - stampmin.home.att.net |
Peridot under a microscope!
image location - microscopy.fsu.edu |
Peridot is typically olive or yellowish green, but can vary from a
medium green to a brownish tone. Generaly the olive tones are more
desireable in the gem trade and the more yellowish stones are
refered to as chrysolite.. Stones are usually transparent and will
have few inclusions. Gemstones of several carats are common, but
larger specimens are rare.
Gem quality Peridot anciently came from Zagbargad or Zeberget (an
island in the Red Sea off the coast of Egypt) or from Burma, now
called Myanmar. It was mined as much as 4000 years ago, and is
mentioned in ancient Hebrew texts as Pitdah. Today about 90% of
Peridot comes from Arizona, with the rest originating in Zeberget,
Myanmar, Pakistan, Brazil, Mexico, and Germany. The ancient sources
were recognized as producing the best quality Peridot, until in 1994,
large stones of an even higher quality were found in the Himalayas of
Pakistan. The rarest Peridot ever facetted and set in jewelry has been
extracted from iron-nickel meteorites called pallasites.
| Composition | (Mg, Fe)2SiO4 | Class | nesosilicate |
| Specific gravity | 3.22 to 3.45 | Refractive Index | 1.65 to 1.69 |
| Birefringence | strong (.037) | Pleochroism | weak |
| Cleavage | poor | Fracture | conchoidal |
| Luster | vitreous to oily | Transparency | transparent to translucent |
| Streak | colorless | Fluorescence | None |
| Crystal system | orthorhombic | Twinning | very rare |
| Hardness | 6.5 to 7.0 | Dispersion | .020 |
| Color | olive green, green, yellow, brown |
| Crystal habit | commonly as compact or granular masses, also as loose or embedded grains, sometimes in volcanic nodules. Crystals are rare, usually as vertically striated prisms. |
| Other
| Peridot is the gem version of the mineral Olivine,
which officially does not exist. Olivine is actually a cross
between two other minerals, fayalite and forsterite. Fayalite and
forsterite are both of the silicate family based on an
(X2)SiO4 composition. In fayalite the X
represents Fe, or Iron, while in the mineral Forsterite the X
represents Mg or magnesium. Olivine's formula is written as
(Mg, Fe)2)SiO4 to show the substitution of
the magnesium and iron. Peridot is usually closer to forsterite
than fayalite, and should contain less than 15% iron, with traces
of nickel and chromium.
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The name "Peridot" is probably derived from the French word "peritot",
meaning unclear, which describes the cloudy nature of the largest
stones, or from the Arabic word "faridat," meaning "gem." Greeks and
Romans referred to it as "topazion" or "topazius," names also used
for topaz. Until recently, "Chrysolite" was also used by some to
refer to Peridot, but this term is now used only to refer to a close
relative of Peridot of a more golden color. It was commonly used to
decorate medieval churches and often carried back to Europe by the
Crusaders for this purpose.
Peridot is said to have been one of Cleopatra's favorites. It was
revered by ancient Hawaiians as the tears of Pele, the goddess of
fire. Legend indicates that Peridot mining on Zeberget was done at
night because Peridot was difficult to see during the day, but its
pale iridescent green was easily illuminated by lamplight at night.
It was due to this quality that the Romans called Peridot the
"evening emerald." Goblets have been carved from the stone, as it is
said to strengthen the power of any medicine drank from it. Pirate's
believed Peridot had the power to drive away evil spirits, but only
if pierced, strung on donkey hair and worn on the left arm.
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