258 REPORT OF NATIONAL MUSEUM, 1899. 



unit of manganese. Settlements are based on analysis made on sam- 

 ples dried at 212, the percentage of moisture in samples as taken 

 being deducted from the weight. . The prices paid at Bessemer, Penn- 

 sylvania in 1894, based on these percentages, were as below: 



Otherwise expressed, the value ranges from $5 to $12 a ton, 

 according to quality and condition of the market. 



It is probable that the total consumption in pottery and glass manu- 

 facture does not exceed 500 tons a year, of which about two-thirds is 

 used in glass making. The amount used in bromine manufacture and 

 the other uses enumerated probably amounts to another 500 tons. 

 The remainder is used in connection with iron and steel manufacture, 

 chiefly in the production of steel and a pig iron containing considera- 

 ble manganese for use in cast-iron car Avheels. In the crucible process 

 of steel manufacture manganese is charged into the pots, either as an 

 ore at the time of charging the pots or it is added as spiegeleisen or 

 ferromanganese at the time of charging or during the melting, usually 

 toward the close of the melting, so as to prevent too great a loss of 

 manganese by oxidation. In the bessemer and open-hearth process 

 the manganese is added as spiegeleisen or ferromanganese at or near 

 the close of the process, just before the casting of the metal into 

 ingots. 



It has been found in recent years that a chilled cast-iron car wheel 

 containing a percentage of manganese is much tougher, stronger, and 

 wears better than when manganese is absent. For this reason large 

 amounts of manganif erous iron ores are used in the manufacture of 

 Lake Superior pig iron intended for casting into chilled cast-iron car 

 wheels. (See also The Mineral Industry, VIII, p. 419.) 



V. CARBONATES. 



1. CALCIUM CARBONATE. 



CALCITE, CALC SPAR, ICELAND SPAR. These are the names given to 

 the variety of calcium carbonate crystallizing in the rhombohedral 

 division of the hexagonal system. The mineral occurs under a great 

 variety of crystalline forms, which are often extremely perplexing to 

 any but an expert mineralogist. The chief distinguishing characteris- 

 tics of the mineral are (1) its pronounced cleavage, whereby it splits 



