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Main Peridotite Hill on Seberged Island

Photo Source : unknown

Large Peridote / Olivine / Forsterite Crystals on Seberged Island, Red Sea, Egypt

Coordinates : 23°36'N , 36°11'E : Seberged (Zabargad) Island, Red Sea, Egypt

To see Seberged island on Google Earth, please click here.


- Peridote on Seberged Island -


Seberged is the island with the many names. This island was known in antiquity as Topazios and later as Saint Johns Island. Nowadays it is known as Seberged or Zabargad with occasional spellings as Zebirget or Zabirgad. While Seberged is only small in size, it is an extremely interesting place in terms of history, geology and biology. In recent times it is also well known among divers, which come here to experience the thrill of a "bottomless" reef face at the outer margin of the island. But Seberged has much more to offer.

The Red Sea is a prime example for the tectonic break up of two continents, e.g. of Africa and Arabia, resulting in a long and narrow ocean known as the Red Sea. But despite the predominant extensionional tectonics involved, we often get alsocontradicting compressional elements of tectonics in the same areas. In the case of Seberged the compressionional forces were strong enough to result in a massive upthrusting of mantle material to the surface of the ocean, finally resulting in the formation of two islands : Seberged and neighbouring small Shark Island.

Hence Seberged has a very complex geology with large slabs of mantle derived rocks scattered in the island, consisting predominantly of fresh peridotites, which hosts lustrous green gemmy peridote crystals up to 10 cm and more. The ancient egypts and greeks knew about these peridote crystals, and mined them for many centuries and the island became famous under the name of 'Topazios' in the ancient world. Later in christian times the name changed to 'Saint Johns Island' before the island became forgotten for many centuries.

Seberged was rediscovered in the 19th century, when geologists explored the old mines and found interesting nickel deposits, which were later mined in the Nasser era around 1960. Recently the diving community "discovered" Seberged and the beautiful reefs surrounding the island, steeply rising 500 m out of oceans depth. And modern geologists became aware of the unique geology on the island which allow a rare opportunity to investigate fresh and unweathered mantle derived rocks.

I had the privilege to have a short visit to remote Seberged in 1994. We visited the remains of the ancient mines and admired the beauty of the turquoise lagoon surrounding the island. Of course we also looked for peridote. We found some small gemmy crystals, mere leftovers of century long mining and hand sorting. But we also saw large opaque olivine crystals in situ embedded in more massive peridotite rock with about 1 meter size ! The crystals are typical "olive" green and display a prismatic habitus. They seldom show idiomorphic crystal faces, but are clearly individual crystals of remarkable dimensions. Pitty, that I didnt took any photos of the crystals. Maybe next time...

For more infomation please read an expedition report to Seberged in 1980, written by Peter Bancroft and published 1984 in his famous book "Gem & Crystal Treasures". here , or go to a new excellent article about the mineralogy and mining history of Seberged by Olav Revheim at Mindat here.

Seberged in a nutshell :

Mineralogy :

Olivine / Peridote / Forsterite

Crystal Size :

Crystals up to 1 meter size, gemmy crystals up to 2o cm, apparenlty formef by late stage hydrothermal fluids, are reported

Geology & Origin :

Several upthrusted blocks of fresh unweathered upper mantle peridotite occur on the island, embedded into a complex faulted metamorphic sequence. The peridotite crystallized in situ in the upper mantle region and was subsequently uplifted to its present location.

Current status :

Seberged Island is not easily accessible. While the outer reef is a popular diving destination, the island as such is considered an environmental protected zone.

Remarks :

Seberged presents an unique opportunity to study fresh upper mantle rocks and their related mineralogy.



Resources and Relevant Weblinks :

For more information on the mineral olivine / forsterite please look at, Webmineral and the german Mineralienatlas.




Peridote Crystal from Seberged Island

Photo Source : BANCROFT, P.(1984)


Seberged Ahoy - first glimpse of the island
and its peridotite hills

Photo Source : lms_namaste on


View of the central peridote hill with light brown reef and turquoise lagoon in forefront.

Photo Source : lms_namaste on


Dive grounds along the "bottomless abyss" - a reef going straight down for 500 meter

Photo Source : lms_namaste on

Geological Map of Seberged Island

Source : Olav Revheim (2014) see main text




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