192 Weed and Pirsson — Bearjpaw Mountains of Montana. 



The chemical composition of this interesting rock is shown 

 in the following analysis by Dr. H. N. Stokes, given in No. I. 



I. 11. III. lY. 



SiO, ._ 5'7-46 57-63 56-58 54-46 



Al^g 15-40 17-53 19-89 19-96 



Fe.O' 4-87 3-46 3-18 2*34 



FeO -87 1-18 -56 3-33 



MgO -_. 1-37 -22 -13 -61 



CaO .__ 2-59 1-35 I'lO 2'12 



Na,0 5-48 5-80 10-72 8*68 



K,0 _. 9'44 9-16 5-43 2-76 



H,O-110° -09) . 



H,O + 110° -82 f ^^^ ^^^ ^^^ 



TiO, -60 -23 ? trace 



CI -20 -08 ? ? 



P,0, -21 trace ? ? 



SO3 -.- -13 



CO, - -13 



Fl trace 



MnO trace trace -47 trace 



BaO -60 not det. 



SrO .-- -16 not det 



Li^O trace trace 



100-42 99-88 99-83 99-46 



= C1 -05 -03 



100-37 99-83 



I. Tinguaite dike from head of Bean Creek, Bearpaw Moun- 

 tains, Montana. H. N. Stokes anal. 



II. Tinguaite dike from Cone Butte, Judith Mountains, Mon- 

 tana. L. V. Pirsson anal. 



III. Tinguaite dike from Hedrum, South Norway (Brogger 

 Grorudit-Tinguait Serie, p. 113). G. Paykull anal. 



IV. Tinguaite dike, Njurjawpachk Umptek Kola (Ramsay & 

 Hackmann, Neph. Syen. Gebiet Kola Fennia, II. No. 2, 1894, 

 p. 158). K. Kjellin anal. 



The marked feature of this analysis is the preponderance of 

 potash over soda; in this respect the rock differs markedly 

 from similar types investigated elsewhere, as may be seen by 

 comparison with the other analyses given. 



The only rock that we can compare with it is that of a dike 

 of tinguaite from Cone Butte in the Judith Mountains, another 

 of the outlying mountain groups of central Montana; the 

 specimen was collected and briefly described by E. S. Dana."^ 



* Rep. Reconnaissance Carroll, Montana, to Yellowstone Park in 1875, Wm. 

 Ludlow, War Dept. Washington, 1876, p. 105. 



