2. •St. John's Island (also known as
Zabargad, Zebirget, Topazios) is the
largest of a group of islands in Foul Bay, Red
Sea in Southern Egypt.
•It covers an area of 4.50 square kilometers
(approx.).
•It is not a quaternary volcanic island, but
rather is believed to be an upthrusted part of
upper mantle material.
•The nearest island is Rocky Island.
• The island is slightly north of the Tropic of
Cancer, and its highest point is 235 meters.
4. Researchers report on peridot mining in
the Red Sea
St. John’s Island or Zabargad, the Arabic
word for peridot, is purportedly the world’s
oldest known source of gem olivine.
Situated in the Red Sea about 45 km.
southeast of Ras Banas on the coast of
Egypt, much has been written about
Zabargad’s unusual geology and modern
workings; however, unequivocal evidence
of an ancient mine has not been reported
until now.
5.
6. The picture indicates Forsterite ( Olivine )
Size 1.3 x 0.7 x 0.4 cm
A gem peridot crystal from the classic locale
for gem forsterite - St. Johns Island in the
Red Sea off Egypt
This ancient locality was mined for peridot or
"night emerald" as it was called, in the time
of the Egyptian pharaohs
This is a locale now long gone and to my
knowledge not collected from after the early
1900 s at latest. In fact, the site is now under
the Red Sea. This is a superb, historic gem
crystal and a fine thumbnail as well
7. In an article appearing in the November /
December issue of MINERVA magazine
(“Egypt’s Evening Emerald,” pp. 16–19),
James Harrell (University of Toledo, USA)
and Elizabeth Bloxam (Monash University,
Australia) provide the first description of
the ancient mine.
Ancient writers identified Zabargad as Ophiodes
(Snaky) and also Topazos, and they called the
yellowish green transparent gem found there
topazos.
8. Peridot appears to have been used sparingly
in the Mediterranean cultures of the
Hellenistic and Imperial Roman periods.
Extant examples are primarily intaglios or
plain, unengraved ringstones and their dates
of manufacture range between 250 BCE and
500 CE.
9. Gem quality peridot specimens, below, from
modern and ancient mines on Zabargad
Island, collected by James Harrell, 2010;
cabochon (12.7 x 9.9 x 3.9 mm.) from
modern mine purchased in Cairo market in
2009. (Photo: Lisbet Thoresen)
10. Specimens of gem
quality peridot from
the ancient mining
site on Zabargad
Island. Collected by
James Harrell, June
2010. (Photo:
Lisbet Thoresen)
11. Commercial peridot and garnierite mining
occurred on Zabargad Island during the first
half of the 20th century, but since then the
island has been abandoned except for the
occasional temporary military camp.
The ancient mine is located on the island’s
southeast shore and consists of roughly 150
surface pits, which individually are up to 20
meters across with adjacent spoil piles as
high as 5 meters. Peridot crystal fragments
up to 1.5 cm across are commonly found on
the surface within these workings.
12. The modern mine reportedly yielded whole
crystals up to 20 cm in length, and crystal
fragments nearly as large as this were
observed by the authors
Similarly large peridot crystals undoubtedly
came from the ancient mine, as well.
Also associated with the mine are the ruins
of stone dwellings, which housed the
miners, and a well that provided them with
water. Pottery fragments, which are
especially common around the well, date
mainly from the 3rd to 1st centuries BCE of
the Hellenistic period with the rest extending
13. The miners and their supplies would have
come from the Graeco-Roman port city of
Berenike, on the Egyptian mainland 80 km.
northwest of Zabargad Island
Mining activity on Zabargad probably closely
mirrored the rise and fall of Berenike’s
fortunes, which peaked in the 1st century
CE, and when this city was abandoned by
the mid-6th century CE, so also was the
peridot mine on Zabargad Island.
14. New analyses of rare earth elements (REEs)
and abundances of
K, Rb, Sr, Ba, Th, U, Ta, and Hf in peridotites
from Zabargad Island, Red Sea, indicate that
light REE-enriched amphibole peridotites in
the northern and central bodies have
undergone a
complex, multistage, metasomatic history
during Red Sea rifting. The metasomatism is
partly attributed to the passage of alkalic
basalts through the mantle lithosphere, which
possibly occurred during the
early, continental-rift history of the Red Sea.
15. The metasomatism also results from the interaction
of the uppermost lithosphere with hydrous crustal
fluids released from thinning continental crust. The
last metasomatic event is associated with the
development of an oceanic hydrothermal system in
the Red Sea, after the continental breakup. The
available data also suggest that the Zabargad
peridotites represent pieces of pan-African
lithospheric mantle (the northern and central
bodies) pierced by asthenospheric material (the
southern body).
16. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 91, NO. B1, P. 599, 1986
doi:10.1029/JB091iB01p00599
Exceptionally fresh peridotite bodies outcrop
on Zabargad Island, an uplifted fragment of
sub-Red Sea lithosphere. The peridotites are
associated with basaltic dikes and are in
tectonic contact with a metamorphic unit and
with post-Mesozoic sedimentary units. The
peridotites can be divided into three main
groups: (1) protogranular spinel Iherzolites
(sp-lherzolites), with average modal
composition ol 65%, opx 16%, cpx 16%,
spinel 3% (2) amphibole peridotites (amph-
peridotites), containing >2% magnesio-
hornblende (3) plagioclase peridotites (pl-
peridotites), containing >2% Ca-plagioclase.
17. Minor outcrops of dunite and wherlite were also
observed. The pl-peridotites and amph-peridotites,
which are found in localized zones or bands within
the sp-lherzolite, show textures ranging from por-
phyroclastic to cataclastic, indicating varying
degrees of tectonic deformation. Olivine and opx
have a rather constant composition in the three
groups, Fo ranging between 87.3% and 90.5% and
En between 88% and 89%, respectively.
Clinopyroxene is chromian diopside but contains
less Na in the pl-peridotites than in the sp-
lherzolites. Both opx and cpx are moderately Al and
Cr-rich, as is typical of mantle-equilibrated
pyroxenes.
18. Spinel has a very low Cr/Al ratio in the sp-lherzolites,
lower than in the pi- and amph-peridotites. Plagioclase
in the pl-peridotites ranges between An 80% and
93%, while traces of it rimming spinel in some of the
sp-lherzolites are more sodic. The amph-peridotites
contain up to 28% magnesio-hornblende and, in some
cases, traces of phlogopite and apatite; opx, cpx, and
spinel are scarce. The major element composition of
the Zabargad sp-lherzolites, their slight light rare
earth element (LREE)-depleted pattern, transition
elements Sc, Ti, Cr, Mn, Fe, Co, and Ni data, together
with modal and mineral chemistry data, are all
consistent with the sp-lherzolites having last
equilibrated in the sp-lherzolite stability field (>9 kbar,
>30 km deep) and representing essentially
undepleted parental mantle material, though some
samples might have undergone minor partial melting
19. The pl-peridotites may represent localized incor-
poration of a melt component by the ascending
Iherzolite body. The amph-peridotites are enriched
in K, LREE, and occasionally in P relative to sp-
lherzolites; they were probably formed by localized
contamination with H2O-rich metasomatic fhids
injected through the Iherzolite body during its
ascent. The Zabargad peridotites were probably
emplaced from the upper mantle into the crust
during the development of the Red Sea rift, i.e., in
post-Mesozoic time
They show affinity with some mantle-derived
oceanic ultramafics, particularly with St. Paul
Rocks in the Atlantic. They could be considered a
sample of oceanic mantle before extraction of the
basaltic oceanic crust
