Mineralogical Description of the Island of Banka. 95 



In the specimens of granite which I collected from this hill, 

 the mica is, upon the whole, very sparingly distributed ; the frag- 

 ments of quartz are of very different sizes, from that of the small- 

 est grain, to crystals nearly an inch in length ; the feldspar is 

 mixed with the other parts in large oblong or rhomboidal fragments 

 which are mostly easily separated, and in many parts occupy 

 the greatest proportion of the mass. In some portions minute 

 particles of schorl are barely perceptible, in some these are uni- 

 formly mixed with the substance of the stone, in others none are 

 to be discovered. 



In all the rocks which I examined, and of which I collected 

 specimens, the mica was, upon the whole, sparingly distributed, 

 and the only occasional admixture was schorl in very small pro- 

 portion. 



The mines of Mampang have been opened within the last 



two years near a small river called Tengalow, which discharges 



itself into the ocean, a little east of Seka: they are situated in 



the granite district, about one mile from the northern shore of the 



island. The miners (at the mine Sunwad) had met the layer of 



ore about ten feet below the surface, it was situated in a valley, 



and pursued nearly the same direction as the bed of the river, 



which was turned from its course, and employed for the purpose 



of washing the ore, as an aqueduct. 



I noticed the following strata : 



L Soil, 2 J feet 



2. A mixture of fine particles of quartz and clay, . 4 " 



3. Detached coarse particles of quartz and feldspar 



with a small portion of clay and some sand, . 3 " 

 At the bottom of this stratum the particles of tin 

 ore become perceptible. 



4. Coarse fragments of quartz and feldspar with small particles 

 °f schorl; this "contained the ore of tin: at the termination the 

 Workmen produced to me the white friable substance above men- 

 tioned, called Kongtay by the Chinese. 



The mines of Tmju belonging to Sungie-bulu and those of 

 Thynhm and Seam, are situated at the southwest extremity of 

 the district of the mines, at no great distance from the road. I 

 Passed along an extensive aqueduct of the mine of Tayu, 

 w hich had lately been constructed. Having left the district of 

 the mines, the road leads through a thick forest, the soil of which 

 is a deep, black, vegetable mould. The country is on the whole 

 descending. Besides several extensive veins consisting of fixed 

 rocks of red ironstone, I observed fragments of this stone wher- 

 ever the stratum of soil was removed by a current of water. In 

 the stockade of Sungie-bulu were collected several large frag- 



