BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 8, PP. 169-182, PL. 14 FEBRUARY 25, 1897 



THE LEUCITE HILLS OF WYOMING * 



BY J. F. KEMP 



(Bead before the Society December 29, 1896) 



CONTENTS 



Page 



General review of the occurrence of leucite 169 



Geographical location of the Leucite hills 1 73 



Previous description of the Leucite hills by S. F. Emmons 173 



Additional notes - 174 



Geological characters 174 



Petrography 175 



Introductory , 175 



Previous observations by Zirkel 176 



Unpublished observations of Cross. 177 



Variety of rock rich in leucite 177 



Varieties of rock with more or less sanidine 178 



Inclusions ! 179 



Petrography of Pilot Butte 179 



Chemical composition 180 



General Review of the Occurrence of Leucite. 



The mineral leucite is not a rock-maker of the first magnitude, but it 

 has nevertheless attracted special interest because of its abundance where 

 found. This latter characteristic places it in the group of feldspathoids, 

 which in a minor way have the same important relations to the classifi- 

 cation of igneous rocks as do the feldspars themselves. It is the general 

 impression that up to 1868 but three leucite localities were known, f 



* In the field-work on which this pacer is based the writer has been assisted by Mr Charles A. 

 Fulton, one of his students, and by Mr O. A. Kennedy, of Ogden, Utah, to both of whom acknowl- 

 edgments are here made. 



t It is stated by E. Kalkowsky in a review of a paper by V. Steinecke, entitled " Ueber einige 

 jimgere Eruptiv-gesteine aus Persien," which was published in the Zeitschrift fur Naturwissen- 

 schsften, iv Folge, Band vi, pp. 1-71, Halle, 1887, and which is not accessible to the writer, that 

 Uoftus had made known the occurrence of leucite near lake Urmia, in Persia, in 1850. ("Aus 

 dieser Gegend hatte bereits Anfangs der fiinfziger Jahre Uoftus das Vorkommen von L,eucit 

 erwahnt.") This would modify the above sweeping statement. See Neues Jahrbuch., 1889, vol. i, 

 p. 438. 



XXV— Bull. Geol. Soc. Am., Vol. 8, 1896 (169) 



