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Characteristics and origin of sepiolite (Meerschaum) from Central Somalia

Published online by Cambridge University Press:  09 July 2018

A. Singer ,
K. Stahr  and
M. Zarei
A. Singer
Affiliation:
Seagram Center for Soil and Water Sciences, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel
K. Stahr
Affiliation:
Seagram Center for Soil and Water Sciences, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel
M. Zarei
Affiliation:
Institut für Bodenkunde u. Standortslehre, Universitat Hohenheim, D-70599 Stuttgart, Germany
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Abstract

Nearly pure sepiolite clay crops out in a playa-like depression near El Bur, Central Plateau region of Somalia. The deposit is associated with the Lower to Mid-Eocene Taleh Formation that includes, besides limestone, dolomite and gypsiferous marls, extensive anhydrite and various evaporites, primarily gypsum. The material was examined by XRD, DTA, IR and EM. The XRD and DTA analyses indicated that from 40 cm down to a depth of 300 cm, the material consists of well crystallized sepiolite, accompanied in some layers by minor calcite and traces of quartz and halite. The chemical composition, determined by XRF, indicated a low-Fe mineral, with the formula: (Si11.888Al0.l12)(Mg7.313Al0.154Fe0.084)O30(OH2)4(OH2)4.x8H2O.

The fibres, arranged in the form of interwoven mats, are straight and have lengths varying between 2-6 µm and widths of 20-40 nm. Commonly, they are aggregated into units of two parallel-lying fibres, with a random orientation against each other, creating a dense network of pores. The high viscosity and external surface area (306-346 m2g-1) of the material, compared to those of the Spanish Vallecas sepiolite, suggest the high industrial suitability of this clay. The extent of the deposit is not known. Lithology and geomorphology indicate a lacustrine, closed basin evaporative environment of formation for this deposit. In contrast to the palaeolacustrine environments of formation of Spanish and Turkish sepiolite deposits, the E1 Bur sepiolite apparently is more recent.

Type
Research Article
Information
Clay Minerals , Volume 33 , Issue 2 , June 1998 , pp. 349 - 362
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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