392 F. A. M'IT,DER THE ORIGIN OF GYPSUM 



here occurs "in lenticular masses from 2 to 1 feet in the center and from 

 50 to 75 feet long, embedded in the gypsum. Crude petroleum has also 

 been reported as occurring in large cells in nodules of gypsum found in 

 the clay which forms a covering for the deposit.^^ 



In Persia and the Near East gypsum is often associated with oil seeps. ^^ 



On the north of the road from Mosul to Bagdad are occurrences where 

 oil seeps from gypsum beds, running out over the road. Oil springs exist 

 in the vicinity of Kifri, about 150 kilometers northwest of Bagdad, where 

 beds of gypsum yield quantities of salt, sulphur, and petroleum. On the 

 Euphrates, in the vicinity of Hit, the natives, with crude working meth- 

 ods, secure about 2,500 tons of asphaltic oil a year from a series of gypsum 

 beds in layers up to two meters thick, intercalated with sandy clays. In 

 western Persia, about 150 miles west of Shustas, seepages yield small 

 amounts of oil for native use. The source is a bed of light yellow loam 

 rich in sulphur and gypsum. According to Harris,^® the anhydrite in the 

 Douglashall mine at Stassfurt is often bituminous. 



Naphtha occurs with the gypsum and salt in the province of Arch- 

 angel. ^° 



The association of gypsum with oil and bituminous shales may be the 

 result of the action of sulphur, which is usually associated with hydro- 

 carbons, on marl or limestone. It may, on the other hand, merely indi- 

 cate that the same seepage conditions that bring the oil to the surface 

 have been instrumental in concentrating and depositing gypsum. 



ALTERATION OF AXIIYDRITE 



J. A. Udden-^ believes that certain extensive beds of anhydrite in Texas 

 have been formed in connection with the dolomitization of the limestone, 

 as the result of a reaction between magnesium sulphate in the circulating 

 solutions and the calcium carbonate in the original sediment. 



Careful observation and study should be directed to the relationships 

 between gypsum and anhydrite. The belief seems to be growing that 

 anhydrite is very often the original mineral from which gypsum has been 

 derived by hydration. 



A. F. Eogers-^ states that "from all the most reliable evidence, it 



" Cole : Gypsum in Canada. Canadian Dept. of Mines, p. 223. 



1* Edmund M. Speilver's review of "Die Turkisch-Persisclien Bi-dolvorkommen." by 

 Schweer, published in Eng. and Min. Jour., August 14, 1920, by permission of Director 

 of U. S. Geol. Survey. 



1" Geol. Survey of Louisiana, Bulletin 7, p. 146. 



=" Fuchs and De Launay : Traite des Gites Mineraux. 



^ The deep boring at Spurr. Bull. Univ. of Texas SGS. p. 67. 



"School of Mines Quarterly, Columbia Univ., vol. xxxvi, no. 2, .January, 1915, p. 141. 



