USEFUL METALS 173 



however that mctasomatic replacement of the limestone more 

 closely approximates to the true explanation of the facts observed. 



According to K. Yamada, antimonial ores occur on the island 

 of Shikoku iu lodes in a sericite schist with quartz as the chief 

 gangue mineral. Magnificient groups of splendent crystals of 

 stibnite that have found their way into many museums occur in 

 the extensive antimony mines in the Province of lyo on the same 

 island. 



In the order of their importance, Bolivia, France, Hungary 

 and Spain are the commercial producers of antimony. 



Geological Horizon. The ores of antimony are not confined 

 to any particular geological horizon. Those in the Appalachian 

 belt are associated with the older crystalline schists. Those in 

 Arkansas occur in the Carboniferous. In Tuscany antimony 

 lodes occur between the Permian shales and the Eocene lime- 

 stones. 



Methods of Extraction. (1) Roasting. Owing to the low 

 fusion point of stibnite, melting easily in a candle flame, the ore 

 is crushed and roasted, the liquated sulphide drawn off in in- 

 clined iron pipes. The sulphide is then roasted in a current of 

 air when the oxide, Sb 2 O3, is formed. The oxide is then re- 

 duced to the metallic state by common salt or scrap iron. The 

 crude metal thus obtained is further refined by roasting with 

 scrap iron. The following reaction may obtain, Sb 2 S3+3Fe = 

 3FeS-r-Sb 2 . The process is applicable to the sulphides of the 

 metal. 



(2) The Crucible Method. Native antimony is crushed and 

 heated in large graphite crucibles with scrap iron. If any sul- 

 phur is present it unites with the iron in the formation of the 

 sulphide of iron as represented in the above equation. The 

 antimony by its higher specific gravity sinks to the bottom of 

 the crucible as a bluish- white crystalline metal. The process is 

 applicable to the native metal and to the sulphide, stibnite. 



(3) The Wet Method. Stibnite is dissolved in hot concentrated 

 HC1 and precipitated from its solution by iron or zinc. It may 

 also be precipitated by pouring into water when the oxychloride, 

 SbOCl is formed. 



(4) The Reduction Process. The oxides of antimony, valentinite 

 and senarmontite, may be reduced to the elemental state by 

 reduction with carbon. 



