Saturday, August 25, 2012


Forsterite (peridotite, chrysolite)
Zabargad was mined in Pharaonic times for greenish-yellowish olivine which was used as a gemstone.

Olivine is one of the most common elements on terrestrial planets and has been found in meteorites as well as in Moon and Mars explorations. However, as olivine reacts strongly with oxygen it is not found in the crust of Earth but only deeper on in the mantle.

Olivine group consists of magnesium-iron silicate. The more magnesium, the greener the color (forsterite Mg2SiO4) and the more iron, the more yellowish the color of the mineral is (fayalite Fe2SiO4).
The island comprises three massives of peridotite, which are rich in the gemstone peridote (olivine). This gem makes the island notable as it is believed to be the first discovered source of peridot, which was called topazios in ancient times, hence the Greek name for the island, Topazios.

Layers of spinel-lherzolites with anhydrous Al-diopside pyroxenites and hydrous Cr-diopside pyroxenites can be found too on the island. The presence of all of these minerals has led to mining on the island which dates back as early as ancient times.
Rich deposits of olivine are commercially mined in the Western coast of Norway where mantle rocks are reached in mine south of Ålesund (Sibelco Nordic). The mineral could be very promising in fighting global warming as olivine is relatively inexpensive and reacts strongly with CO2 (Peter Koehler). However, it is currently not in such use and can be therefore be called one of the most underrated minerals of mother Earth.

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