H. S. Washington — Solvsbergite and Tinguaite. 181 



second place. The hornblende is considerably lower, and in- 

 stead of glaucophane (ferrous also) predominating over the 

 riebeckite molecule, the latter surpasses the former, its compo- 

 sition being expressed by the formula Kb 9 Grl 2 . It is hence 

 essentially a riebeckite rather than a glaucophane. 



I. II. III. IV. Y. 



SiO a 73-93 71-65 73-35 74*35 70'15 



Ti0 2 0-18 trace 0"65 



A1 2 3 12-29 13-04 14-38 8'73 10*60 



Fe 2 3 2-91 2-79 1*96 5-84 5'77 



FeO 1-55 1-80 0-34 1*00 1'74 



MnO trace trace 0'22 0*52 



MgO 0-04 trace 0-09 0*07 0'35 



CaO 0-31 trace 0'26 0-45 0-72 



BaO none 



Na 2 4-66 6*30 4'33 4'51 5'30 



K 2 4-63 3-98 5-66 3'96 4-09 



H o 0-41 1-10 0-25 trace 



100-91 100-66 



100-3' 



99*38 99-89 

 H. S. Washing- 



I. Granite, Hard wick Quarry, Quincy, Mass. 

 ton, anal. Sp. gr. 2*642 at 22° C. 



II. Soda Granite, Houguatten, Norway, Brogger, Gror. Ting. 

 Ser. 127. L. Schmelck, anal. 



III. Paisanite, Paisano Pass, Texas, Osann, Tsch. Min. Pet. 

 Mitth., xv, 439, 1895. Osann, anal. 



IV. Grorudite, Varingskollen, Norway, Brogger, op. cit. 48. 

 Sarnstrom, anal. 



V. Grorudite, Grussletten, Grorud, Norway, Brogger, op. cit. 

 48. V. Schmelck, anal. 



la. Ha. Ilia. IVa. Va. 



Riebeckite 12*3 10- 6- 



Glaucophane 2*0 4- 



JEgirite 21-6 22*5 



Albite 27-7 40- 32- 19-1 29-5 



Orthoclase 27-2 23- 35- 21-8 24-5 



Quartz 30*2 23- 27' 37*5 23'5 



Accessories 0-6 0'5 



In column II is given an analysis of a typical soda granite 

 of Norway, which, according to Brogger is composed of alkali 

 feldspar, quartz and blue hornblendes, with small amounts of 

 magnetite, zircon, apatite, etc. It is closely parallel to our 

 granite, the only differences of note being lower Si0 2 and cor- 

 respondingly higher Na Q 0. The results of a roughly approxi- 

 mate calculation based on Brogger's analysis and description 

 are given in Ila, the hornblende being assumed from his de- 



