CHEMICAL COMPOSITION OF VARIOUS LEUCITES. 181 



Localities and Authorities. 



I. Rock from Leucite hills ; R. W. Woodward, analyst. Fortieth Parallel Survey, 

 vol. i; table opposite page 604, vol. ii, page 237. Duplicate determinations of the 

 alkalies afforded Na 2 0, 1.57 ; K 2 0, 10.63. 



II. Rock from Leucite hills ; Pawel, analyst, for F. Zirkel. Sitzungsberichte der 

 Siichsische Gesellschaft der Wissenschaften, Mathematische-Physikalische Classe, 

 1877, page 239. 



III. Leucite- tinguaite, Magnet cove, Arkansas , R. N. Brackett, analyst, for J. F. 

 Williams. Annual Report Arkansas Geological Survey, 1890, page 287. Dense 

 rock. 



IV. Leucite-tinguaite, Magnet cove, Arkansas ; J. F. Williams, analyst. Idem. 

 Rock with phenocrysts ; contains also rare earths, 0.48; SrO, 0.09; MnO, 0.44; 

 Li 2 0, trace; CI, 0.53; S0 3 , 0.52. 



V. Leucite-tinguaite, Bearpaw mountains, Montana ; H. N. Stokes, analyst, for 

 Weed and Pirsson. American Journal of Science, September, 1896, page 196. 

 Contains also Ti0 2 , 0.20; Kl, 0.27; CI, 0.70; S0 3 , 0.67 ; P 2 O 5 ,0.06; SrO, 0.07 ; 

 BaO, 0.09; Li 2 0, trace. 



VI. Leucitite, Bearpaw mountains, Montana ; H. N. Stokes, analyst, for Weed 

 and Pirsson. American Journal of Science, August, 1896, page 147. Contains 

 also Ti0 2 , 0.83; Fl, trace; CI, 0.04; S0 3 , trace; P 2 5 , 0.80; CuO, strong trace; 

 NiO, 0.04; CoO, strong trace ; MnO, 0.22; BaO, 0.50; SrO, 0.16. 



VII. Leucite-absarokite, Ishawooa canyon, Wyoming ; J. E.Whitfield, analyst, 

 for J. P. Iddings. Journal of Geology, vol. iii, 1895, page 938. Contains also 

 TiO 2 ,0.8S; MnO, 0.13 ; P 2 5 , 0.59; CI, 0.18. 



VIII. Leucitophyr, Lower California, v. Chrustschoff. Tschermak's Minera- 

 logische und Petrographische Mittheilungen, vol. vi, 1884, page 160. Contains 

 alsoTi0 2 , 0.15; P 2 5 , 0.19. 



IX. Leucite rock, Montalto, Italy, Antonio Verri. Bolletino della Societa 

 Geologica Italia, vol. vii, 1888, page 49. The analysis is taken from the Neues 

 Jahrbuch., 1891, vol. i, page 271. 



An examination of numbers I and II at once shows marked peculiari- 

 ties. The range in silica is high for basaltic leucite rocks, of which VI 

 and VII illustrate the usual values, although somewhat low. The alu- 

 mina is low, the lime fairly high, and the magnesia remarkably high, 

 exceeding the lime. The alkalies are high, and the great richness in 

 potash as compared with soda is worthy of comment. It is clear from 

 the analysis that a very exceptional rock would result from this magma. 

 Number IX is the nearest parallel to it in general composition. The 

 other analyses illustrate the ranges of the leucite rocks that have been 

 thus far discovered in the west. 



