1875.1 



463 



[Swallow. 



The analysis gave : — 

 Silica SiOn 



Alumina Al 2 3 . 

 Peroxide of Fe 2 3 

 Potash K 2 

 Soda Na,0 



MgO, CaO 



66.53 



25.09 



trace 



4.67 



.39 



2.64 



traces 



99.32 



These percentages taken in connection with the physical characters 

 point to the Pinite group. Taking the alumina as a basis of calcula- 

 tion the results are: — 



Si0 2 .... 



Na 2 

 H 2 G. 



56.93 

 33 



6.11 

 .51 



3.45 



100.00 

 -which would leave 22.56 per cent, of silica as quartz. 



The calculated percentages most nearly agree with Agalmatolite 

 from China as given in Dana's Mineralogy. 



The north wall is a rather fine grained, very compact, dark gray- 

 ish green rock, containing numerous small crystals of pyrite. Sp. Gr. 

 2.71. Fusible on the edges to a black slag which is magnetic. Equally 

 attacked by hydrochloric, nitric and sulphuric acids. Effervesces 

 with cold dilute acid, which dissolves a portion of the iron as well as 

 lime. When powdered and examined under the microscope it seemed 

 to be composed of three minerals; one a pale yellowish green resem- 

 bling the south wall, an olive green transparent mineral sometimes 

 bladed or showing cleavage in one direction, and very small opaque 

 fragments appearing black. After treatment with acids the green 

 mineral was wanting. 



Analysis gave: — 



S . 



.14 



co 2 . . . . 



. 3.31 



H 2 G 



5.53 



FeO .... 



7.54 



A1 2 3 . . . 



22.32 



CaO .... 



. 2.58 



Si0 2 



15.01 



Na 2 + K 2 



.85 



Insoluble . 



42.59 



99.59 



