4(5 TIN DEPOSITS OF THE YORK REGION, ALASKA. [no. 229. 
has been found at another locality. At El Paso,' wolframite occurs 
with the ores, and feldspar is replaced by cassiterite. 
In Virginia 5 good tin prospects have been found on the headwaters 
of Irish Creek, Eockbridge County, in quartz lenses and stringers in 
granite, which itself is intrusive in metamorphic schists. Associated 
minerals are wolframite, mispickel, iron pyrites, quartz, and beryl, 
with small amounts of siderite, limonite, chlorite, muscovite, damour- 
ite, and fluorspar. 
In Wyoming, 6 at Nigger Hill, in the northwestern portion of the 
Black Hills, cassiterite has been found in a granitic area that is similar 
in geological association to that at the Etta mine. 
CONDITIONS AND METHODS AT THE LARGE TIN MINES OF THE 
WORLD. 
Since the tin from newly discovered sources must come into compe- 
tition with the product of established mining districts, a comparison 
with the mining conditions in the older districts will be useful in esti- 
mating the value of the newer ones. For this purpose the following 
notes have been compiled from the most recent publications on the 
tin deposits of the world, and a brief bibliography of these is presented 
on pages 55-56. 
The greater part of the world's supply of tin is obtained from allu- 
vial deposits. Over three-fourths of it comes from alluvial deposits 
in the Malay Peninsula, otherwise known as the Straits Settlements, 
and the islands of Banca and Billiton, off the north coast of Sumatra, 
the former region producing about half of the tin of the world. A 
large amount is produced from alluvial deposits in Australia, while in 
Cornwall, Saxony, and Bolivia most of the tin ore is obtained from 
vein deposits in the bed rock. 
M \LAY PENINSULA.'' 
The Malay Peninsula, in which the Straits Settlements tin deposits 
are located, consists of a central axis of rugged hills running north 
and south, with occasional subordinate or diverging axes and isolated 
peaks. The whole region is covered by a jungle of tropical vegeta- 
tion so dense that the roads and trails have to be hewn through. In 
the tin regions the main range is composed of granitic rocks, occasion- 
ally cut by f eldspathic and other dikes, while in some places are found 
gneissic and schistose rocks, with occasional areas of a white, highly 
crystalline limestone. 
Tin ore occurs in nearly every part of the western side of the Malay 
a Weed, W. H., The El Paso tin deposits: Bull. U. S. Geol. Survey No. 178, 1901. 
fcRolker, C. M., Production of tin in various parts of the world: sixteenth Ann. Rept. V. S. Geol. 
Survey, pt. 3, 1895, pp. 523-525. 
cRolker, C. M., cit., p. 530. 
dThe following notes regarding the Malay tin deposits are taken almost verbatim from R. A. F. 
Penrose, Tin deposits of Malay Peninsula: Jour, of Geol., vol. 11, 1903, pp. 135-154. 
