TIN, DISCOVERIES OP, IN AMERICA. 



801 



lion. The amendment providing for the estab- 

 lishment of a railroad commission received 178,- 

 864 affirmative and 71,885 negative votes; the 

 amendment relating to county roads received 

 134,463 yeas and 73,037 nays. Eleven Demo- 

 cratic members of Congress were chosen 



TIN, DISCOVERIES OF, IN AMERICA. 

 Twenty-five years ago the world's production of 

 tin was not more than 15,000 tons a year. Now 

 Australia alone produces more than that quan- 

 tity, and the imports into the United States from 

 Great Britain are worth over $25,000,000 every 

 year. For several years the Government of the 

 United States made a standing offer of a bonus 

 of $250,000 for a discovery of tin. Small de- 

 posits were found in California and Georgia, but 

 not in quantities large enough to affect the mar- 

 ket. In 1884 tin was found in paying quantities 

 in the vicinity of Harney's Peak', in the Black 

 Hills, in Dakota. The Black Hills form an oasis 

 of rock and forest in a sea of grass. They are 

 arranged like an irregular ellipse, extending 

 about 120 miles from northwest to southeast, and 

 .about 50 miles wide. They take their name, 

 which is translated from the Sioux, from the 

 dark foliage of the pines with which they are 

 covered. In almost every direction extend tree- 

 less plains for hundreds of miles. Harney's 

 Peak, 7,442 feet high, is an intrusion of granite, 

 and it forms the core,*or axis, of the great uplift. 

 Immediately surrounding the peak is a region of 

 metamorphic slates and schists, bordered by the 

 various members of the sedimentary rock, up to 

 the cretaceous, lying in rudely concentric rings 

 or belts of varying width, and dipping away on 

 -all sides of the elevatory axis. The tin ore is 

 found in the granite region. The granite occu- 

 pies an area measuring about 12 miles by 8, the 

 principal mass being Harney's Peak itself. As 

 a line of separation from the'gneissic rocks, the 

 granite is decided and distinct ; its grain is ex- 

 ceedingly coarse, each constituent being highly 

 crystalline and aggregated by itself that is, the 

 quartz, the feldspar, and the mica are found in 

 large masses of crystals. This peculiar forma- 

 tion has led to the location of numerous mica 

 claims, which are worked with fair profit ; and 

 the development of the mica claims led to the 

 discovery and investigation of the tin ores, which 

 occur in the same rocks. The tin is found in the 

 class of rock called greisen, which in this region 

 differs from the variety found at Vaulry, France, 

 in having albite instead of quartz with the mica ; 

 but in the other characteristics of crystallization 

 and mineralization it resembles that of Vaulry 

 and that occurring in the tin dykes of New South 

 Wales. The greisen is uniformly impregnated 

 by the tin, the crystals of ore varying in size, 

 those about a quarter of an inch in diameter be- 

 ing most abundant. The general appearance of 

 the rock is that of a mass of white spar and yel- 

 lowish mica crystals, well spotted with black 

 grains and large crystals of tin, like a pudding 

 or cake full of raisins and currants. The ore it- 

 self is the oxide of tin, known as cassiterite, and 

 there are three forms of occurrence in general. 



1. Granular, disseminated through greisen rock ; 



2. Massive ; 3. Placer, or stream tin, this latter 

 being the result of the decomposition and disin- 

 tegration of rock through ages of weather influ- 

 ences. Some oxides and carbonates of copper 



voi,. xxx 51 A 



are found in accretion, but they are not constant- 

 ly associated. The greisen rock is found all 

 through the granite region of Harney's IVak 

 Ihe stream tin is common, and it is distributed. 

 like gold, in earth that results from thedaoooh 

 position of gold-bearing rock. It is found in tin- 

 dirt on all the streams flowing from the Jlarn.-v 

 range on the east, west, and north sides; and i't 

 has long been known, although not as tin, to the 

 miners who were sluicing for gold. In the gold 

 sluices it appears as a heavy black mineral, in 

 grams from the size of a pea to that of a hen's 

 egg. It is found in the streams as far east as 

 Harney City, as far west as Hill City, and on the 

 north as far as Sheridan. The outlying granite 

 being intrusive, extends to great depths, while 

 the area and distribution of the mineralized por- 

 tions of the granite, taken in connection with 

 the known placer deposits, go to show that there 

 exist in the Harney's Peak region large quanti- 

 ties of tin so placed that they can be econom- 

 ically and profitably worked. Much of the tin- 

 bearing rock can be easily obtained. It can be 

 quarried from the surface instead of being dug 

 for and followed underground. Some of the 

 veins measure more than 50 feet in width. The 

 rock can easily be crushed, the ore concentrated, 

 and the metal worked into bars of pure tin. The 

 process for extracting the stream tin resembles 

 placer mining for gold, although it is much 

 rougher, the metal being in larger fragments and 

 larger quantities. The stream tin yields about 

 75 per cent, of pure tin, while an average of only 

 2 per cent, is obtained from the ore in Cornwall, 

 England. The supply seems to be inexhaustible, 

 for the stream tin is merely the waste that has 

 worked down from Harney's Peak. 



Other mines are on Iron creek, in the vicin- 

 ity of Rapid City, South Dakota, but the pro- 

 cess of gaining the ore is by shafts. The ore 

 is hoisted from the main shaft and dumped first 

 into an ore bin of 200 tons capacity, located far 

 up the mountain over the mill. From this bin 

 it is conveyed to the mill by a wire-rone bucket 

 tramway, the loads going down the hill to the 

 mill and hauling the empty buckets back to the 

 mine. The ore buckets deliver their contents me- 

 chanically into a 175-ton ore bin above and back 

 of the mill. The large lumps of ore are crushed, 

 then passed through a drier to a set of improved 

 Cornish rolls, and thence elevated to a set of 

 rotary sizing sieves. From the sieves the finer 

 sizes are conveyed to a set of paradox concen- 

 trating tables, and the coarser sizes to common 

 Hartz jigs. The screens, jigs, and concentrators 

 separate completely all the mica, quartz, and 

 feldspar, leaving clean concentrates of cassiter- 

 ite, or oxide of tin, ready to be smelted into tin 

 bar. The concentrates are for the present being 

 shipped to Chicago to be smelted. The main 

 vein measures from 28 to 32 feet in width at the 

 outcrop, and over 40 feet in the lower working. 

 Assays and tests from the different workings 

 give an average of over 3 per cent, of metallic 

 tin, while specimen rock is often blasted that will 

 yield over 30 per cent, of the white metal. 



Arrangements are progressing, both in this 

 country and in Europe, for working mines in 

 North Carolina, where tin ores are found to oc- 

 cur in a formation varying from 1 to 2 miles in 

 width and extending about 28 miles in length. 



