The Norite of Sierra Leone

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Abstract
I. Introduction. The norite of Freetown (Sierra Leone) was briefly described by G. Gürich in 1887, and in 1918 Prof. S. J. Shand translated Gürich's work, adding a few notes. I had the opportunity of making a detailed examination of this norite, as part of an investigation into the mineral resources of Sierra Leone; and in the course of this work it was found that the norite exposed around Freetown was only one end of a huge noritic complex which made up the whole mountain-mass of the Colony. Moreover, during the examination several features of considerable interest were observed, including the assimilation of one phase of the norite by another, the well-developed banding in the norite, the segregation of the iron-ores, and the sequence of the minor intrusions. These features, together with an important series of intergrowths of the common minerals, will be described in the course of this paper. The investigation into the mineral resources of the Colony, with especial reference to the iron-ores, formed part of the work of the Geological Survey of Sierra Leone during the latter part of 1918 and during 1919. (2) Physiography of the Area. 2 The Colony is a mountainous peninsula adjacent to the undulating low ground which forms the southern part of the Protectorate. Its mountains rise steeply from a narrow coastal plain to a height of nearly 3000 feet; this plain is continuous with that of the mainland, and is due to a Pleistocene uplift of a little over 300 feet. It

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