pyrolite, rock consisting of about three parts peridotite and one part basalt. The name was coined to explain the chemical and mineralogic composition of the upper mantle of the Earth. The relative abundances of the principal metallic element components (except iron) are similar to those in chondritic meteorites and in the solar photosphere. Accordingly, it is reasonable to assume that to a first approximation these abundances are applicable to the entire mantle.