178 II. & Washington — Solosbergite and Tinguaite. 



refraction small, and the grains might be mistaken for quartz 

 were it not for the color. Although no pleochroic halos were 

 seen, the mineral is referred to comierite. It may possibly be 

 a foreign inclusion, brought up from below, but this point 

 cannot be settled. 



There are also seen a number of small, slender, light yellow- 

 ish needles, which extinguish parallel to their length, and in 

 some cases are very faintly pleochroic, with the absorption 

 e ^> (o. These are apparently apatite, though small irregular 

 flakes of a similarly appearing substance do not show the usual 

 form of this mineral, and they may possibly be rosenbuschite, 

 which is said to occur in North American nepheline-syenites.* 



The results of a chemical analysis by the writer are given in 

 No. I. 



r. it. in. iv. v. 



Si0 2 64-28 62-70 64/92 64'33 64-21 



Ti0 2 0.50 0-92 trace 



A1 2 3 15-97 16-40 16-30 17'52 16-98 



Fe 2 3 2-91 3-34 3'62 3 06 6'69 



FeO 3-18 2-35 0-84 0'94 



MnO trace trace 0-40 0*35 



MgO 0*03 0-79 0-22 0"34 0'18 



CaO 0*85 0*95 1*20 0'56 0-49 



BaO none 



Na 2 7-28 7*13 6*62 7*30 5*13 



K 2 G 5-07 5-25 4-98 4"28 4'41 



H 2 0, 110° .... .... 0-04 



H 2 0, ignit 0-20 0-70 0'50 0-95 1-00 



P.O. 0-08 trace 



100-33 100 53 99-60 99'67 99-09 



I. Glaucophane-Solvsbergite. Dike 184. Andrew's Point, 

 Cape Ann, Mass. H. S. Washington anal. 



II. Katoforite-Solvsbergite. Lougenihal, Norway. Brogger. 

 Grorudite-Tinguaite Serie, 80. L. Schmelck anal. 



III. Aegirite-Solvsbergite, Solvsberget, Gran, Norway. Brog- 

 ger, op. cit., 78. L. Sckinelck anal. 



IV. Aegirite-Solvsbergite (Acmite-Trachyte), Crazy Mountains, 

 Montana. Wolff and Tarr, Bull. Mus. Comp. Zool., xvi, 232, 

 1893. W. H. Melville anal. 



V. " Aegirite-Trachyte." Kiihlsbrunnen, Siebengebirge. Cited 

 in J. Roth, Gesteins analyse, 1861, 21. Bischof anal. 



The chief characteristics are medium acidity, high alkalies, 

 especially soda, rather high FeO, and low MgO and CaO. 

 These characters are well expressed in the mineral composition, 

 which, since the rock is noncrystalline and of simple composi- 

 tion, is readily calculated to be as follows : 



* Rosenbusch, Mikr. Phys., i, 510, 1892. 



