THE NONMETALLIC MINERALS. 175 



before. To these types belong the sulphur deposits of Utah, Cali- 

 fornia, Nevada, and Alaska in the United States, as well as those of 

 Mexico, Japan, Iceland, and other volcanic regions. Sulphur is derived 

 from the sulphate of lime (gypsum or anhydrite) through the reducing 

 action of organic matter. The sulphate, through the loss of its oxygen, 

 becomes converted into a sulphide, which, through the carbonic acid 

 in the air and water, becomes finally reduced to hydrogen disulphide 

 with the formation of calcium carbonate. 



According to Fuchs and De Launay 1 there is formed at the same 

 time with the hydrogen disulphide a polysulphide, which in its turn 

 yields a precipitate of sulphur and carbonate of lime. The maximum 

 amount of sulphur which would thus result from the decomposition of 

 a given amount of gypsum is stated to be 24 per cent. This method 

 of origin is illustrated in the celebrated deposit of Sicily, where we 

 have the sulphur partially disseminated through and partly interbedded 

 with a blue-gray limestone. (See Specimen No. 60932, U.S.N.M.). 

 Beneath the sulphur beds as they now exist are found the older gyp- 

 seous beds, which through decomposition have yielded the materials 

 for the lime and sulphur beds now overlying. 



With these Sicilian sulphurs occur a number of beautiful secondary 

 minerals, as celestite (Specimens Nos.. 60866, 60869, 60877, U.S.N.M.), 

 calcite (Specimens Nos. 60854, 60865, 60871, U.S.N.M.), aragonite 

 (Specimen No. 60859, U.S.N.M.), and selenite (Specimen No. 60857, 

 U.S.N.M.). 



Sulphur derived directly from metallic sulphides is of little economic 

 interest. Kemp states 2 that masses of pyrite in the calciferous strata 

 on Lake Champlain may yield crusts of sulphur an inch or so thick, 

 and it is not uncommon to find small crystals of the mineral resulting 

 from the alteration of galena, as described by George H. Williams 3 

 at the Mountain View (Maryland) lead mine. 



The minute quantities of sulphur found in marine muds are regarded 

 by J. Y. Buchanan* as due to the oxidation of metallic sulphides, 

 which are themselves produced by the action of animal digestive secre- 

 tions on preexisting sulphates, mainly of iron and manganese. 



Localities. The principal localities of sulphur known in the United 

 States are, in alphabetical order: Alaska, California, Idaho, Louisi- 

 ana, Nevada, Texas, Utah, and Wyoming. With the possible excep- 

 tion of those of Idaho and Texas, and that of Louisiana, these may 

 all be traced to a solfataric origin. The Alaskan deposit, 5 according 

 to Dall, are best developed on the islands of Kadiak and Akutan. 



1 Trait6 des Gites Mineraux et Metalliferes, I, p. 259. 



2 The Mineral Industry, II, 1893, p. 585. 



3 Johns Hopkins University Circulars, X, 1891, p. 74. 



Proceedings of the Royal Society of Edinburgh, XVIII, 1890-91, p. 17. 



5 Alaska and its Resources, Boston, 1870. 



