part 4] NOEiTE or sierra leone. 313 



■differences in the texture of the component parts, and by the 

 rough weathering and dari^er colour of the bands and streaks of 

 the younger rock. Nevertheless, where relations between the 

 different rocks are very complex, it is not always possible to assign 

 the banding to one cause rather than to another. 



Important Exposures. 



•.(i) Godrich Point. — Four elongated domes of coarse norite, long- axes 

 running east and west, rise through a roof of normal norite. One 

 of them, forming Godrich Point, cuts across the banding of the 

 normal norite, and is itself pierced by a dolerite-dyke ; another, 

 5 yards long and 3 yards wide, sends out a number of little tongues 

 into the normal norite. 

 <(ii) Point north of No. 2 Town. — Striking complex of coarse and 

 normal norites displayed ; blocks and fragments of normal norite 

 measuring several feet across are enclosed within the coarse norite ; 

 a few of them are angular, with sharp boundaries, but the greater 

 number show corroded outlines with large re-entrant curves. Many 

 normal norite -fragments are small and ill-defined, and in some 

 places are, with the enclosing rock, drawn out into wavy streaks. 

 There are also several exposures of a rock of mixed texture due to 

 permeation of normal norite by coarse norite. 



(iii) Toke P o i n t .—Intrusion phenomena well exposed. 



(iv) York foreshore. — Large area of coarse norite richly impregnated 

 with magnetite. In it are numerous stoped blocks of normal norite 

 measuring as much as 10 yards in diameter ; they exhibit all stages 

 of disruption, corrosion, and absorption, some of them having been 

 liberally eaten into by the invading magma, and others thoroughly 

 impregnated by it (see PL XVII, fig. 1). Large outcrop also of a 

 rock consisting of an intimate mixture of older and younger 

 norites. Farther north, a dolerite-dyke is seen cutting older and 

 younger norites. 



(v) Point on the south side of Whale River, York. — One ex- 

 posure shows coarse dolerite invading and shattering normal norite ; 

 the junction is crossed by a later fine-grained dolerite-dyke. 



' (vi) John Obey Poin t. — A large intrusion of coarse norite : its junction 

 with the normal rock on the north side is almost 100 yards wide, 

 and shows a great intermingling of the two types. Innumerable 

 veins, tongues, and masses of the coarse pierce the normal rock, 

 which shows signs of a very high temperature and much absorption. 



!(vii) Samuel Island. — Numerous intrusions of younger norite along the 

 foreshore. The margins exhibit banding and streakiness due to the 

 intermixture of the two rocks. 



(3) The Beerbachite. 



In the northern half of the Colony, and principally in the 

 Freetown district, occur intrusions of a fine-grained, granular 

 TOck,i dark grey when fresh and weathering to pale grej^ ; it some- 

 times shows a faint parallel structure in thin section. It consists 

 ■essentially of labradorite, with subordinate h3''persthene and mag- 

 netite, and its specific gravity is 3 •08. A partial analysis of a 



1 The ' norite-aplite ' of Prof. S. J. Shand, Geol. Mag. 1918, pp. 22, 23 ; he 

 classifies the rock as melanocratic norite {iUq — micronorite). 



