A very large peridot about the size of a very large potatoe ( probably weighing
over three hundred carats) was bought by a French gem dealer more than thirty years
ago. Some years later the stone appeared on the cover of a famous magazine with
Brook Shields as the model. This stone remains the finest and biggest cut peridot
to this day. Until recent years, the finest peridot came from Burma. Then there
was the discovery of smaller sizes and more yellowish colored peridot "gravels"
from the Indian reservations in Arizona. They were however more included with the
typical "lily pad" like inclusions. Some were cuttable and most were tumbled and
drilled to make necklaces.
Then came China and its productions. The Chinese materials were maninly smaller
in size under 3 carats and lighter in shades. Still none came close to the Burmese
peridot in color instensity or brilliance. Then came the mines in Pakistan which
were producing some of the finest ever found. The colors were deep and clear. The
crystal purity contain almost zilch brown. They were on par if not superior to Burma
peridot. Alas, the mines in Pakistan/Afghanistan border were interupted with the
war on Osama Bin Laden and production was sporadic and quantities dwindled. Mostly
German dealers got ahead start and managed to get a few good deals until travelling
became hazardous and if not impossible in the embattled war zone.
Lately, world demand has pushed up prices and remains strong for the time being.
Also known as olivine, it is called fosterite when Mg is present and fayalite when
iron is present. Peridot however is the term most commonly used in the gem trade
to refer to this gem. Fosterite shows green hues to pale lemon yellow. Fayalite
displays green, yellowish green, amber brown, brown, olive, green. The color of
peridot is due to ferrous iron. The best green is supposed to contain an iron content
of about 12 to 15%. More Fe would result in a darker brownish color. Very bright
green has shown traces of Cr.
Chemical formula is Mg2SiO4-Fe2SiO4. Mn is rarely present. Crystal habbit is orthorhombic,
crystals are rare especially well formed ones, usually striated, elongated and eroded,
often as rounded pebbles. Luster is vitreous. Hardness is 6.5 - 7. Cleavage is imperfect
to weak. Fracture is conchoidal. Brittle. Birefringence is strong ranging from 0.035
to 0.052. Distinct doubling of facet junctions can be observed. Refractive index
is 1.635 to 1.654 and may vary with chemical composition.
Egypt and Norway are known to have produced peridot but not in commercial quantities
and not in recent times. Cat's eye and star variety have been reported. Peridot
is the birthstone for August and remains a big favorite among gem enthusiats and
collectors. Its unique green has been a source of universal appeal for this fine