390 F. A. AVILDER THE ORIGIN OF GYPSUM 



indorse this view, the Virginia gypsum deposits as now found are cer- 

 tainly not of salt-pan origin. 



E. W. Stone'' believes that the gypsum of Florida has been deposited by 

 springs, and the evidence seems to point definitely to this conclusion. 

 The tremendous masses of gypsum found in the "domes" in Louisiana 

 and Texas are regarded by G. D. Harris and some others as the work of 

 upward-moving waters which carried gypsum in solution. 



ALTERATION OF CARBONATE 



Before 1877, when Ochsenius published the result of his observations 

 in connection with sea-water, gypsum was generally regarded as an alter- 

 ation product derived from limestone. Sulphurous waters are abundant 

 and Avidespread and their ability to change limestone into hydrated lime 

 sulphate is admitted Avitliout question. Numerous illustrations may be 

 cited. A striking case at Spatsum, British Columbia, is described by 

 L. H. Cole.'" Gypsum-bearing rocks occur on the hills forming the west 

 bank of the Thompson Eiver. The rocks of the district are schists, gray- 

 wackes, and some limestone. Cole says : 



"The surface material consists of a badly disintegrated mass of mica schists, 

 limestones, and shales, with frequent nodular lumps of white gypsum of vary- 

 ing size. After passing through this altered material, which has been lightly 

 recemented. the tunnel cuts through a band of very pure, massive white gyp- 

 sum, which ju'oved by analysis to be almost a theoretically pure gypsum. This 

 band, however, was only 5 feet wide, with a very light gray or white highly 

 altered hydromica schist, together with some altered limestone, for the hang- 

 ing wall and for the rest of the length of the tunnel." 



0. M. Knode, of the United States Gypsum Company, visited this spot 

 and found a tunnel 40 feet long driven into a bed of crystalline limestone. 

 Sulphurous water originating at a point higher up was seeping through 

 this body of limestone. The whole face of the tunnel Avas moist and 

 slimy from a deposit of gypsum and sulphur. Analyses of the rock along 

 the sides of the tunnel gave from 12 to 100 per cent of gypsum. Knode's 

 conclusion was that the entire limestone ledge Avas being altered to 

 gypsum. 



There seems to be a frequent association of gypsum Avith hydrocarbons. 

 The oil domes of the Gulf coast have attracted a good deal of attention, 

 and the fact that great masses of gypsum and salt enter into their struc- 

 ture is well knoAvn. F. L. Hess, in his report on the gypsum deposits of 



" Gypsum deposits of the United States. U. S. Geol. Survey r.ulletin 0!>7, 1020. 

 ^" Gypsum in Canada, pp. 95, 96. 



