This is a very strange book indeed. The author starts with the premise that it is very difficult to determine the origin and evolution of the crust using the generally accepted compositions for the upper mantle. He concludes that the upper mantle is of a sialic composition, but comprises dense forms of the constituents quartz and feldspar (coesite, stishovite, hollandite and/or wadeite), hence the ‘densialite’ of the title, with Mg, Fe and Ca only minor. Such a conclusion raises many difficulties, of course, amongst which are how basalts can to be produced from a sialic mantle. The answer is an...

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