138 R. A. F. PENROSE 



amount of gold occurs on the eastern side, while very little has 

 been found on the western side. Hence the eastern slope is 

 known as the "gold region" and the western slope as the "tin 

 region." 



To the southeast of the peninsula, tin is mined on the islands 

 of Banka and Billiton, which are owned by the Dutch. In 

 Banka the mines are worked by the government and are more 

 productive than those of Billiton, which are operated by an inde- 

 pendent company. The occurrence of the tin on these islands 

 is said to be similar to that on the peninsula. Tin is found also 

 on the island of Sumatra, off the southwest coast of the Malay 

 peninsula, but has not been worked to any great extent. Its 

 occurrence is said to be somewhat like that of the peninsula, 

 and the fact that the production is small is said to be due to the 

 unexplored character of the country and to the constant troubles 

 between the Dutch authorities and the natives. 



General geology of the Malay tinregiofis. — The Malay peninsula 

 consists of a central axis of rugged mountains, with occasional 

 subordinate parallel or diverging axes and isolated peaks. The 

 whole region is covered by a jungle of tropical vegetation so 

 dense that the roads and trails have to be hewn through it with 

 an ax. In the tin regions the main range is composed of granitic 

 rocks, occasionally intersected by feldspathic and other dikes, 

 while in places are found gneissic and schistose rocks, with 

 occasional areas of a white, highly crystalline limestone. The 

 granite is mostly of a gray color and is composed of quartz, 

 feldspar, and biotite or hornblende, or both. There seem to be 

 all gradations from a granite with biotite and no hornblende to a 

 granite with hornblende and no biotite. Black tourmaline is a 

 common constituent of the granite in the neighborhood of the 

 tin deposits. The limestone is generally a highly crystalline 

 marble of a white color, occasionally streaked or spotted with 

 gray. No fossils were seen in it, and it is said that none have 

 been found. Such as may have existed seem to have been 

 destroyed by the metamorphosis of the rock, though a more 

 thorough search might reveal traces of them. The limestone is 

 especially abundant in the Kinta district, though also found 



