USEFUL Ml .7 M/.s 181 



Hi-rnatlino County, California. The principal vein varies from 

 a few inches to 8 ft, in width. In 1SD2 this mine was a producer 

 of pig tin and bid fair to be of considerable comnn -n -ial impor- 

 tance. It has, however, since that date been only a small 

 producer. 



(5) The Alaskan Belt. In this district tin occurs in lodes and 

 placers in the Seward Peninsula. According to F. L. Hess, the 

 ores occur: (1) In quartz veins traversing phyllite schists; (2) 

 in quartz porphyry dikes traversing limestones; (3) in dis- 

 seminations in the greisenized granitic rocks. The ores are 

 associated with calcite, fluorite and the lithium mica, zinnwalditc. 

 A. H. Fay, (Trans. A. I. M. E., 1907) mentions one deposit as a 

 contact between limestone and granite associated with much 

 tourmaline. This area bids fair to be of some commercial 

 significance. 



Foreign Countries. Two foreign deposits of tin ores are worthy 

 of special consideration for they have been the largest producers 

 of this useful metal. The first of these is Cornwall and Devon, 

 England. The second is found in the Federated Malay States. 



According to Thomas and MacAlister, the tin deposits in the 

 former district are intimately associated with five large granite 

 batholiths. Two of these at West Cornwall, England, are 

 intruded in sediments of Ordovician age. Two in central and 

 east Cornwall, in rocks of Devonian age. One in Devonshire 

 in terranes of both Devonian and Carboniferous age. 



The association of tin and copper ores are better illustrated at 

 Cornwall, England, than in any other locality. The association 

 of the tungsten and arsenic minerals with those of copper and tin 

 is such that it leads to the conclusion on the part of some that the 

 ores are of identical age. 



The cassiterite poitions of the lodes, however, occur in the 

 older parts of the veins and appear to have been the first min- 

 erals formed. In other cases the cassiterite, chalcopyrite, ar- 

 senopyrite and wolframite are so intimately associated that it 

 renders successive deposition a matter of doubt (Fig. 100). 



The most important tin deposits of the world are found in the 

 Federated Malay States. The leading states in production are 

 Selangor, Perak, and Pahang. According to the State Geologist, 

 Scrivenor, the origin of the tin lodes and their association with 

 greisenized granite is akin to those in England. However, much 

 of the tin mined is found in placers. The Kinta Valley is one 



