Vol. 70.] TOPAZ-BEARIXG EOCKS OF GUXOXG BAKAU. 



365 



commenced, the whole of the peak was covered with dense vegetation. 

 It is now the scene of considerable mining activity, and is a striking 

 tribute to the perseverance of the two well-known Pahang miners, 

 Mr. A. H. Bibbv and Mr. J. Buxton, to whom I am indebted for 

 assistance in keeping pace with developments in the Chinchong 

 Valley since 1904. I am also indebted to Mr. W. M. Mason for 

 valuable help on the Selangor side of the mountain. 



The history of the development of Gunong Bakau is noteworthy. 

 In 1904, or perhaps earlier, Messrs. Bibby & Buxton found in 

 the Chinchong Valley numerous boulders of a rock consisting 

 essentially of quartz, topaz, and cassiterite. The percentage of 

 tin-ore was sufficient to stimulate a search for the source of the 

 boulders, and in 1908 a lode was found on the north side of the 

 valley, but it was not the topaz-bearing rock. The prospectors 

 were finally rewarded by finding the topaz- and cassiterite-bearing 

 rock in situ close to the top of G-unong Bakau, and it was proved 

 later to extend to the Selangor side of the mountain and up to 

 its summit. 



II. Outline of the Geologt of G-u^ong Bakau. 



The geology of this part of the Main Range of the Peninsula 

 has been kept In view, so far as circumstances permitted, ever since 

 1904 ; but it Avas not until October and November, 1912, that 



Fig. 2. — Diagram showing the relations of the 'porpligritic 

 granite to the two intrusive rocks. (See p- 366.) 



itt 



[1 = Porphyritic granite ; 2 = Quartz-topaz rock ; 3 = Topaz-aplite. 

 The central quartz -topaz vein has not been proved to exist as yet.] 



it was possible to arrive at definite conclusions. I have no 

 hesitation in saying that these conclusions would not have been 

 possible, but for the extensive operations of the tin-miners and the 

 assistance so readily granted by them. 



Gunong Bakau is composed of porphyritic granite into which 

 two rocks have been intruded, one after the other. The first rock 



