104 abstracts: mineralogy 



system CaO-MgO-Si02 and which had caused the earher investiga- 

 tions to be viewed with suspicion. Tridymite is unstable at its melting 

 point and this unstable melting occurs at 1670 ± 10°. Artificial 

 tridymite made from quartz could not be melted owing to the rapidity 

 of the tridymite-cristobalite inversion, but a sharp melting was ob- 

 tained with natural material. Since this unstable melting point is 

 below that of cristobalite, there can no longer be room to doubt that 

 cristobalite is the high temperature form of silica. R. B. Sosman. 



GEOLOGY. — Asphalt deposits and oil conditions in southwestern Arkan- 

 sas. Hugh D. Miser and A. H. Purdue. U. S. Geol. vSurvey 

 Bull. 691-J. Pp. 271-292, with maps. 1918. 



There are seven asphalt deposits in Pike and Sevier counties, 

 Arkansas. The asphalt occurs in the Trinity formation of I.owe, 

 Cretaceous age which rests on upturned edges of Carboniferous limestone 

 and sandstone. Doubtless the asphalt is a residue of crude petroleum 

 whose lighter and more volatile parts have escaped by evaporation. 

 This petroleum is believed to have been derived from the Carboniferous 

 rocks underlying the Trinity formation, near the base of which the 

 asphalt is found. The geologic structure is not favorable to accumula- 

 tion of petroleum, and the few wells that have been sunk for oil have 

 not found it in commercial quantity. R. W. Stone. 



GEOLOGY.— J/a/zaw Icucitic lavas as a source of potash. Henry 

 S. Washington. Met. and Chem. Eng. 18: 65-71. January 

 15, 1918. 



This paper attempts an evaluation of the total amount of potash 

 that is present in the lavas of the six chief Italian volcanoes along the 

 west coast that have erupted leucitic lavas, which are therefore high 

 in potash. 



It is considered that in these volcanoes Italy possesses one of the 

 largest if not the largest of the visible supplies of potash known to 

 exist. Some other silicate rock sources of potash are briefly discussed, 

 especially the Leucite Hills in Wyoming and the belt of glauconite 

 that extends from New Jersey into Virginia. R. B. S. 



MlNBRAhOGY. —Augite jrom Stromholi. S. Kozu and H. S. Wash- 

 ington. Amer. Journ. Sci. 45: 463-469. June, 1918. 



This paper records the optical characters and chemical composition 

 of the augite crystals that were being thrown out of the volcano of 



