V 



THE NONMETALLIC MINEBALS. 



193 



Pyrite on decomposing in the presence of moisture in the ground 

 sometimes gives rise to an acid sulphate of iron. This may attack 

 aluminous minerals when such are present, giving rise thus to solutions 

 of sulphate of iron and alumina, which come to the surface as "alum 

 springs," or, if no alumina is present, merely as iron or chalybeate 

 springs, which are of more or less medicinal value. The presence of 

 such sulphates in a soil is readily detected by the well-known astrin- 

 gent taste of green vitriol and alum, even where the quantity is not 

 sufficient to appear as a distinct efflorescence. Impregnation of these 

 salts in soils are by ignorant persons sometimes assumed to be of great 

 medicinal value, and the writer has in mind a case in one of the Southern 

 States, in which the aqueous leachings of such a soil were regularly 

 bottled and sold as a specific for nearly all the ills to which the flesh is 

 heir, though prescribed especially for flux, wounds, and ulcers. (See 

 also under Alum, p. 416.) 



BIBLIOGRAPHY. 



W. H. ADAMS. The Pyrites Deposits of Louisa County, Virginia. 



Transactions of the American Institute of Mining Engineers, XII, 1883, p. 527. 

 WILLIAM MARTYN. Pyrites. 



Mineral Resources of the United States, 1883-84, p. 877. 

 J. H. COLLINS. The Great Spanish Pyrites Deposits. 



Engineering and Mining Journal, XL, 1885, p. 79. 

 E. 1). PETERS. A Visit to the Pyrites Mines of Spain. 



Engineering and Mining Journal, LVI, 1893, p. 498. 

 FRANK L. NASON. Origin of the Iron Pyrites Deposits in Louisa County, Virginia. 



Engineering and Mining Journal, LVII, 1894, p. 414. 

 M. DRILLON. The Pyrites Mines of Sain-Bel. 



Minutes of Proceedings of the Institute of Civil Engineers, CXIX, 1894-95, p. 

 470. 



7. MOLYBDENITE. 



A disulphide of molybdenum having the formula MoS 2 , = sulphur 

 40 per cent, molybdenum 60 per cent. 



NAT MUS 99 13 



