srU'HIDKS, AHSKXIDKS, ANTIMONIDKS 



in a blende from Freiberg, Saxony. Specimens containing these 

 rare elements arc very dark in color, as that from Koxbury, Con- 

 necticut. Sphalerite is found under the same conditions and in the 

 same formations as galena, which is its constant companion, with 

 the exception that zinc sulphide is more soluble than lead sulphide 

 and in many cases in the oxidized zones the zinc has been curried 

 away in solution, leaving the galena. The oxidation products of 

 sphalerite are ealamine and smithsonite, which are ores of the su- 

 perficial areas of zinc deposits. In weathering these may be redis- 

 solved and carried down by the percolating waters. This is well 

 substantiated by the analyses of the mine waters at Freiberg, 

 where it was estimated that the discharge in the valley carried 479 

 kilograms of zinc per day, or 175,024 kilograms per year. In 

 undisturbed deposits such solutions of zinc are reprecipitated either 

 by pyrite, marcasite, or organic matter as a sulphide, or by replace- 

 ment in limestones as a carbonate. When sphalerite is formed, 

 these reactions take place at low temperatures, as wurtzite, the 

 hexagonal zinc sulphide, is the stable form at high temperature. 

 Simple crystals of sphalerite occur in the dolomites of the Bin- 

 nenthal, and beautiful specimens are obtained at Santander, 

 Spain. 



In the United States sphalerite is widely distributed in the lime- 

 stones of the Mississippi valley, and the regions of contact of lime- 

 stones with igneous rocks ; all deposits of sphalerite mined for the 

 zinc alone are of these characters. Southern Missouri and the 

 Leadville district, Colorado, both blende deposits, produced 175 

 thousand of the 280 thousand tons of ore mined in 1909. Sphaler- 

 ite also occurs, but of minor importance, in the metalliferous veins 

 of rocks of all ages. 



Zinc is used in innumerable ways ; as a metal it is a component 

 of brass, white metal, and german silver. It is used in roofing in 

 galvanizing iron to prevent rusting, and in the zinc boxes as a reduc- 

 ing agent to precipitate gold from the solutions in the cyanide pro- 

 cess; as an oxide in paint, and at the present time is to a large 

 extent displacing white lead. Artificial sphalerite is formed when 

 a solution of zinc is heated in a sealed tube with hydrogen sulphide, 

 at higher temperatures. In fusions, as of precipitated zinc sul- 

 phide with potassium carbonate and sulphur, or with calcium fluo- 

 ride and barium sulphate, the hexagonal form of ZnS, wurtzite, is 

 formed. Sphalerite when heated to bright redness is changed to 

 wurtzite. 



