170 



BULLETIN OF THE 



gravity of fragments, determined by Westplial balance and Thoulet 

 solution, was between 2.570 and 2.572. 



The following analyses of the feldspar (I.) and the rock (II.) were 

 made in the laboratory of the U. S. Geological Survey at Washington 

 by Dr. Thomas Chatard. 



H»0 at 110° C. 

 H.,(J at red heat 

 Sibj . . . 

 TiO/ . . 

 P2O5 . . 

 Al.O^ . . 



FeO . 



MnO . . 



CaO . . . 



MgO . . 



K2O . . 

 Nap 



I. 



Feldspar. 



.0-1 



.37 



G5.GG 



20.05 



traces 



traces 



.13 



.07 



18 



G.'JS 



G.5G 



IIL 

 Gmelin, No. 



SiOo G5.90 



10.4G 



41 



28 



Al/)3 



CaO 



MgO 



K,0 



. . . . , . G.55 



Ka.O G.U 



1 '^ 



H^O 



Specific gravity 2.587. 



II. 



Keratophyre. 

 .91 



1.28 



70.23 



.03? 



.OG 



15.00 



1.99 



.24 

 .33 



.38 

 4.99 

 4.98 



IV. 



No. 2. 

 G5.19 

 19.99 



.63 



.48 



•7.03 



7.08 



.34 



It is evident from the analysis and optical properties that this is a 

 triclinic soda-potash feldspar of remarkable purity, and veiy evenly 

 balanced percentages of Na and K, belonging to the anorthoclase gi'oup 

 of Itosenbusch. For comparison, analyses (III. and IV.) by Gmelin 

 are a])pended uf anorthoclase from the augite syenite of Norway (Brog- 



* The TiOj wai not very ]iurr, aud its jircauiict, is not aLsolutuly ct-rtaiu. 



