TIN DEPOSITS OF THE MALA V PENINSULA 1 4 1 



white, gray, or red sandy or gravelly clay, often of a mottled 

 character, containing numerous small quartz fragments about the 

 size of a pea, derived probably from the decay of granite and in 

 part from quartz veins, together with pebbles and bowlders of 

 granite, gneiss, schist, pegmatite, limestone, etc. The alluvium 

 in the hills-, however, nearer its source, varies more in character, 

 distinctly reflecting, in different places, the nature of the differ- 

 ent rocks from which it has been derived. Frequently the allu- 

 vium is much stained with iron, and carries layers and masses of 

 rusty ferruginous material consisting partly of sand cemented by 

 iron, and partly of masses of granite and quartz with iron pyrites 

 rapidly oxidizing and forming a brown mass. Sometimes the 

 alluvium contains large quantities of vegetable remains and partly 

 lignitized wood. 



The dense tropical vegetation has given rise to large quanti- 

 ties of organic acids in the soil, and these have often leached the 

 iron from the tin alluvium, leaving a clear white or gray mass, 

 while in other places not so much exposed to this influence the 

 gravel is still discolored. This is especially true of the upper 

 parts of the deposits, which have often become entirely bleached, 

 while the deeper parts are still heavily impregnated with iron. 

 The waters in most of the mines are heavily charged with iron, 

 which is deposited on the sides of the pits and shafts, showing 

 that chemical action is still very active. 



The tin occurs in the alluvium in different ways. Sometimes 

 it is scattered through it from top to bottom in comparatively 

 uniform quantities ; sometimes it is in layers of rich ore sepa- 

 rated by layers of lean or barren ground ; sometimes it is richest 

 on the bed-rock, and at other times higher up in the deposit. As 

 a general rule, however, there is a covering, or " overburden " as 

 it is called, of barren alluvium from 10 to 40 feet or more in 

 thickness, and the tin ground is found beneath this. The best 

 alluvium occurs immediately at the foot of the mountains. 

 Higher up it is often richer, but of small extent, while farther 

 away it is thicker, but of lower grade. The ordinary tin-bearing 

 strata vary from i to 30 feet in thickness, though sometimes 

 they reach over lOO feet. At Gopeng, the Gopeng Tin Mining 



