310 J. B. Scrivenor — Malayan Clays & Mesozoic Granite. 



The two sections occur on the east side of the Kinta Valley, one 

 on the land worked by the Tekka Company, Ltd., the other on the 

 land worked by the Societe des Etains de Tekka. Eoth these mines 

 lie to the north of Gopeng (vide sketch-map with the Geology and 

 Mining Industry of the Kinta Valley). 



The Tekka. Company Section. 



On the Tekka Company's land the Grondwana clay near the granite 

 is of a deep-red colour. Boulders of considerable size are rare in the 

 clay, in fact the only big boulders I have seen in situ on this mine 

 are those of corundum previously described. Lately, however, I have 

 seen some good sections with small boulders bearing a striking 

 resemblance to Boulder-clay. At one part of the mine, newly opened 

 up, the clays can be followed for a distance of about 80 yards right 

 up to a well-exposed junction with the granite, which is here soft 

 owing to its being rich in kaolinite and also to the eflPect of weathering. 

 Perhaps the kaolinite was partly formed by weathering. 



At a distance of about 30 feet from the junction the clay shows no 

 sign of alteration, but within that distance coloured streaks appear, 

 that might in some places be described as folise, and increase as the 

 granite is approached, until at the junction the clay, instead of being 

 a uniform deep-red colour, is a roughly foliated and banded mass of 

 red, black, white, and yellow streaks, and is traversed by small, hard 

 veins of blue tourmaline, which are not easily observable until the 

 clay is broken up. PL XXIII, Fig. 2, is a photograph of a portion 

 of the clay about 8 feet from the granite. PL XXIII, Fig. 1,^ is 

 a photograph on a larger scale of similar altered clay. The black 

 streaks were found to contain iron and manganese. Mineral matter 

 heavier than 2*8 (specific gravity) separated from the altered clay in 

 bulk was found to be chiefly blue tourmaline, but comprised a few 

 grains believed to be secondary corundum and hercynite. 



Near by this section the clay is traversed by white veins which are 

 fairly hard and fine-grained. Some are as much as 6 inches thick, 

 but the majority are smaller than that. Sections and separations 

 show them to consist of white mica and fluorite as a fine mosaic of 

 irregular flakes and grains, with minute grains and acicular particles 

 of corundum that form veinlets in the mosaic, and a small quantity of 

 another mineral believed to be a spinel. The corundum in these 

 veins must not be confounded with the corundum boulders. It was 

 clearly brought into being by the influence of the granite, whereas 

 the big corundum boulders are detrital components of the clay. 



The granite junction is irregular and, apart from the evidence of 

 alteration, leaves no doubt in the writer's mind that the granite was 

 intruded into the clay. 



The Societe des Etains de Tekka Section. (Plate XXIV.) 

 This section is even better than that just described. In the mine 

 a large intrusive mass of granite with tourmaline veins has been 

 disclosed. On either side, as seen now in section, it falls away at 

 an angle of about 45° and is in part fairly hard. On the north side 

 of the granite a big face of clay has been exposed for some time, 

 ^ The scale of inches on the Plate refers to the upper figure (Fig. 1). 



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