Evaluation
of Tertiary shales in Cairo environs, Egypt, for industrial applications:
Mervat S. Hassan
Central Metallurgical Research and Development Inst., Helwan, Cairo, Egypt |
Tertiary shales in Cairo and its environs are
examined for detailed mineralogy, geochemistry and evaluation for industrial applications.
Samples were collected from 4 stratigraphic successions: G. Qattamia (Upper Eocene), G.
ElKhashab (Oligocene), G. Molahiz (Miocene) and Minia ElSharifa (Plio-Pleistocene). The
mineral analyses showed the dominance of monovalent/divalent cation saturated smectite
followed by disordered kaolinite and traces of illite. Quartz and feldspars are the most
common non-clay minerals especially in PIio-Pleistocene clays. Calcite, gypsum and
halite are subordinate.
Chemically, the samples are predominated by SiO2 and Al2O3,
followed by Fe2O3 and MgO. The content of CaO, K2O and Na2O
are subordinate. The histograms for Fe2O3 and MgO suggest that smectite is the main bearer
of Fe2O3 and MgO. The high content of CaO and Na2O
especially in the Upper Eocene clays, is attributed to the presence of gypsum, calcite and
halite respectively. In addition Na2O and CaO are partly in the interlayer
positions of smectite.
Checmical data, technologic specifications and operational characteristics indicate that
the Miocene clays are essentially monovalant-cation saturated smectite of very fine size
and high surface area, therefore have economic potential as bentonites. The other clays
have little or no economic potential as bentonites and they do not meet OCMA
specifications for drilling fluids therefore should be beneficiated before application.
The ceramic behavior of the investigated samples revealed that Maadi clays are
non-refractory clay with low vitrification temperature related to the relatively high
levels of soluble minerals. The other samples are refractory clays and are suitable for
building-brick manufacture. The processing of Miocene clays is made possible by adding
plasticity reducing agents (sand and/or grog).
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