Swallow.] 



464 



[March 17, 



The insoluble portion was fused with carbonate of soda and found 

 to be a silicate of somewhat similar composition as the south wall. 



Soluble portion. 







S 



.25 



SiO, 



C0 9 . 



5.60 



A1 2 3 



H 2 () . 



9.67 



CaO 



Na,0, K . 



1.50 



MgO 



Si0 2 . " . 



26.25 



Na 2 3 



FeO . . . 



13.19 





A1 2 3 . . 



39.03 





CaO . 



4.51 





Insoluble portion. 



K 9 



66.44 



26.73 



6.10 



traces 



.80 



100.07 



99.90 



The composition of the soluble portion does not agree with any 

 described species and may be owing to a mixture of two or more, 

 although the microscopical examination seemed to indicate a definite 

 mineral. Siderite is perhaps present here. 



Siderite is quite abundant in the vein rock, especially in connection 

 with the blende. Among the specimens are 1st, a black variety con- 

 taining traces of lime and magnesia with some manganese and slight 

 traces of lead and copper. 2d. A yellowish gray of nearly the same 

 composition minus the lead and copper. 3d. A nearly pure w r hite 

 variety traversing quartz. This was subjected to examination. Lus- 

 tre like feldspar. The analysis gave : — 



Quartz as impurity 



FeC0 3 



MnC0 3 . 



MgCOg 



CaCO, . 



.72 



46.84 



6.49 



8.83 



34.32 



undet. 



98.20 



The per cent, of magnesia and lime is unusually high. Monheim's 

 analysis of the Altenberg mineral which approaches this more nearly 

 in composition than any other given by Dana, is as follows : — 



FeC0 3 

 MnC0 3 

 CaCO, 



64.04 

 16.56 

 20.12 



