USEFUL METALS 167 



One in the arsenical gold ores of California and the other at 

 Monte Cristo, Washington, where auriferous sulphides, realgar 

 and orpiment are mined and the white arsenic of commerce is 

 manufactured. 



At Deloro, Ontario, arsenopyrite occurs in large beds with a 

 quartz gangue cutting pre-Cambrian schists. This deposit has 

 been successfully worked for some time both for gold and for 

 the arsenic which is converted into white arsenic. The ore also 

 occurs in fissure veins with a quartz gangue in Grimsthorpe, 

 Ontario. The ores here are not so highly auriferous as at 

 Deloro. 



According to Thomas and MacAlister, the presence of arsenical 

 pyrites in some of the largest tin mines of the west of England 

 is remarkable. The lodes belong to the pneumatolytic group of 

 ores. Under similar circumstances the ore is found in the tin 

 mines of Saxony and Bohemia. Workable deposits of arsenical 

 ores are found also in Turkey. 



Geological Horizon. Arsenical ores are found from the pre- 

 Cambrian to the Ordovician in the modes of occurrence suggested. 

 Recent arsenical deposits are not of workable dimensions. 



Methods of Extraction. The Roasting Process . Native arsenic 

 and its sulphides are crushed and heated in long earthenware 

 retorts into whose mouths are fitted earthenware receivers. The 

 arsenic volatilizes, and condenses as a compact crystalline solid. 

 This product is redistilled in a current of air when the arsenic 

 is converted into the white oxide, the form in which it generally 

 appears in the marts of trade. 



The Electric Furnace Process. The Arsenical Ore Reduction 

 Company of Newark, New Jersey, has established anelectrical fur- 

 nace for the treatment of arsenopyrite, commercially known as mis- 

 pickel. The ore is subjected to the intense heat of the furnace in 

 an atmosphere of nitrogen. The iron present in the arsenopyrite 

 unites with the sulphur in the formation of a ferrous sulphide, 

 which is drawn off as a liquid mass. The arsenic is distilled and 

 condensed as a white powder. The cost of the treatment of 

 such ores with 46 per cent, of arsenic is estimated to be less than 

 25 cents per hundred weight. 



Sources of the Arsenic of Commerce. (1) Arsenic is obtained as 

 a by-product in the treatment of the ores from various tin mines, 

 especially in England. (2) From tin, copper and tungsten ores 

 intimately associated with arsenic. (3) From the treatment of 



