ROCK ANALYSES 



399 



Table 1. — Analyses of the Six main Rock Types from the Border to the Center 





I. 



II. 



III. 



IV. 



V. 



VI. 



Si0 2 



53.38 

 20.22 

 1.56 

 1.99 

 0.29 

 3.29 

 7.89 

 6.21 



3.43 



50.96 



19 67 



7.76 



0.36 

 4.38 

 7.96 

 6.77 



1.38 



0.52 



49.70 

 18.85 

 3.39 

 4.32 

 2.32 

 7.91 

 5.33 

 4.95 

 1.09 

 0.25 

 1.33 



41.75 

 17.09 

 6.35 

 341 

 4.71 

 14.57 

 6.17 

 3.98 

 0.62 

 0.28 

 0.58 



38.93 

 15.41 

 5.10 

 4.24 

 5.57 

 16.49 

 5.27 

 1.78 



J 5.20 



| 1.62 



Trace. 

 0.35 

 0.02 

 0.89 



36.51 



Al 2 O s 



8.22 



Fe,0» 



8.29 



FeO 



3.31 



MgO 



8.19 



CaO 



18.85 



Na 2 



2.10 



K 2 



1.08 



H.,0 (ignit.) I 





H 2 (110°) i 



TiO., 



1.40 

 3.11 



X 





2.10 



MnO 



Trace. 



Trace. 



Trace. 



Trace. 

 1.09 



Trace. 



P„0- 





CI 





0.25 





0.03 



FeS 2 



1.77 







6.03 















100.03 



100.01 



99.44 



100.60 



100.87* 



99.22 



I. Foyaite, Diamond Jo quarry ; Brackett and Smith, analysts. Williams: Op. 

 cit., p. 238. 



II. Leucite-porphyry, near Diamond Jo quarry ; Noyes, analyst. Williams: Op. 

 cit., p. 276. 



III. Shonkinite, below school, west border ; Washington, analyst. 



IV. Ijolite, below Doctor Thornton's ; Washington, analyst. 



V. Biotite-ijolite, near Baptist church ; J. F. Williams, analyst. Williams: Op. 

 cit., p. 226. 



VI. Jacupirangite, northeast of Magnet Cove ; J. F. Williams, analyst. Williams : 

 Op. cit., p. 227. 



II is of the leucite-porphyry f near the Diamond Jo quarry. This is 

 composed of leucite, or rather pseudo-leucite, phenocrysts, often of large 

 size, lying in a dark, fine grained, hplocrystalline groundmass of nephe- 

 lite, sharply automorphic brown garnets, diopside, and segirine, with very 

 little orthoclase, titanite, magnetite, apatite, and probably sodalite. 



III is of the rock which Williams calls " fine grained nepheline-syenite," 

 from below the school-house near the western border. It is a rather fine 

 grained, mottled whiteand black rock, composed of orthoclase with nephe- 

 line, diopside with borders of segirine, some greenish hornblende, rather 

 abundant beautifully sharp crystals of titanite, and accessory apatite and 

 magnetite. It will be seen that in chemical composition this rock closely 



* Williams gives 100.57. 



f Williams and Rosenbuseh call this syenite. Its structure is by no means granitic; it may be 

 called leucite-porphyry provisionally, 



