no. 1726. ON SAND-BARITES FROM EGYPT— POGl /.'. 19 



In 1900 Delkeskamp gave an extensive paper on sand-barites in 

 the Wetterau and Rheinhessen districts of Germany, in which he 

 described rosettes and concretionary forms from the Tertiary sand- 

 stones. The concretions are sometimes hollow and contain barite 

 crystals. 



In 1901, Beadnell & found numerous specimens of "crystal- 

 lized barytes-sandstone " in the Dakhla Oasis of Egypt. These 

 are briefly described as tabular crystals, often intergrown into 

 masses of various sizes, and having a specific gravity of 3.25 and 

 silica content of 55 per cent. In the same year Mackie c cited the 

 occurrence of arenaceous barite in the form of nodules disseminated 

 through the Triassic sandstone along the coast of Elginshire, England. 



In 1902, Delkeskamp d included in a second paper an account of 

 the sand-barites from Rockenberg and Vilbel, Wetterau; and 

 Kreuznach, Rheinhessen. In Rockenberg occur well-developed 

 rosettes or "roses," often uniting in extensive groups; and larger, 

 spherical concretions, frequently slightly intergrown. e The Vilbel 

 forms are prominently tabular and simpler. The Kreuznach indi- 

 viduals are mostly spherical and possess an inner radial structure; 

 they are frequently intergrown and show strange shapes, resembling 

 pears, turnips, etc. From 20 to 30 per cent sand is present in the 

 various occurrences. 



In 1906 Nichols^ described sand-barites from near Muskogee, 

 Oklahoma. These are rosettes made of intergrown plates and are 

 somewhat rounded by wind action. The content of angular quartz 

 fragments is 37 per cent. The U. S. National Museum possesses 

 specimens from near Bavaria, Saline County, Kansas (Cat. No. 

 85275), which are very similar to those from Oklahoma. 



Occurrence. — The specimens to be herein described were collected 

 by Dr. A. Ilrdlicka, of the U. S. National Museum, while on an anthro- 

 pological expedition to Egypt in 1909. They occur in the Lybian 

 Desert, and more particularly in the central part of the Kharga 



a R. Delkeskamp, Schwerspatvorhommnisse in der Wetterau and Rheinhessen und 

 ihre Entstehung. Notizbl. Ver. Erdkunde, vol. 21, 1900, pp. 47-83. 



b II. J. L. Beadnell, Dakhla Oasis: Its topography and geology . Egypt. Geol. Surv. 

 Rept., 1901. 



<' \Y. Mackie, The occurrence of barium sulphate and calcium fluoride as cementing 

 Bubstances in the Elgin Trias. Etep. Brit. Ass. Adv. Sci., 1901, |>. 649. 



d R. Delkeskamp. Ueber die Krystallisationsfahigkeit von Kalkspat, Schwerspat, 

 und Gyps bei ungewohnlich grosser Menge eingeschlossenen Quarzsandes. Zeitschr. 

 Naturw., Halle, vol. 75, L902, |>|>. 185-208. 



«The National Museum possesses specimens from Rockenberg, Cat. No. 80612. 



)\\. W. Nichols, Sand-barite crystals from Oklahoma. \ln New forms of concre- 

 tions.] Pubi. Field Col. Mus., Geol. Ser., publ. Ill, vol. 3, 1900, pp. 31-35. 



