256 ECONOMIC GEOLOGY 



of safes, where the results are extremely satisfactory. The body 

 of the safe is cast in one solid piece. The door which is also of 

 manganese steel is grooved and fitted into the doorway so accu- 

 rately that the joint is perfectly tight and explosive liquids are 

 not successfully forced into the safe. The ordinary files and 

 chisels are useless in finishing the safe, therefore air-driven abra- 

 sive wheels are employed. The groove fits so perfectly that all 

 attempts to open the safe by burglars' tools and high-grade ex- 

 plosives have thus far failed. 



In a classification of the uses by means of the purity of the ores 

 the following division may be made. (1) The very low-grade 

 ores are used in the chemical trade, in the manufacture of glass, 

 brick and pottery. (2) The high-grade ores are used in the 

 manufacture of spiegeleisen and ferromanganese. 



Manganese is also used in the manufacture of manganese 

 bronze, which consists of manganese and copper with or without 

 iron. It is furthermore utilized in silver bronze, which consists 

 of manganese and copper, together with silver, aluminum and 

 zinc. It is also used in the manufacture of titanium alloys. 

 Many of the complex alloys of which manganese steel is a con- 

 stituent are capable of wide industrial application. 



In spite of the numerous uses of manganese ores, and the wide 

 application of manganese steel, the production of manganese in 

 the United States is comparatively small. The most important 

 eastern locality is Virginia. Most of the manganese for domestic 

 consumption is imported from Brazil. Cuba entered the race 

 for the first time in 1900. It is therefore to be expected that 

 Cuba will continue to be an important contributor of high-grade 

 manganese ores for the market of the United States. 



Zinc; Its Properties, Occurrence and Uses 



Properties. Zinc, symbol Zn, is a bluish-white crystalline 

 metal. At a temperature of 100 it becomes soft, and at 150 

 it is ductile and malleable. It can therefore be readily rolled 

 into sheets or drawn into wire. The sheets and wires do not 

 become brittle again upon returning to the normal temperature. 

 At a temperature of 300 C., zinc can be rendered pulverulent. 

 The metal tarnishes readily in moist atmosphere, becoming 

 coated with a basic carbonate of the metal. In dry atmosphere 

 at the ordinary temperature it remains permanent. Ordinary 



