52 



The analysis of this specimen yielded the following results 

 (i). No. II, introduced for the sake of comparison, is the 

 composition of a specimen from Mitterberg, Tyrol, quoted from 

 Dana : — 



* Obtained by difference. 



The composition of the mineral as given above is represented 

 by the formula 4 PeCOa + MgCOs. From the composition 

 of this specimen, and from that of others which have from time 

 to time ])assed through my hands, it w^ould appear that the 

 siderite of this colony is chiefly of the magnesian variety. 



BlOTITE. 



This mineral is of very common occurrence in the Torke's 

 Peninsula Mines, the most notable being the Yelta Mine, 

 where it occurs in large masses. I have not met with it in 

 distinct crystals, but only in massive aggregations of cleavable 

 scales. The colour is generally dark green to nearly black ; 

 thin laminse are green by transmitted light. 



The specimen selected for analysis was from the Yelta Mine. 

 It had a specific gravity of 2-9. 



The result of the analysis was as follows : — 



DRIED AT 100° C. 



Silica ... ... ... 40-28 



99-12 



Clay. 



The following analysis is that of a specimen of clay obtained 

 from Teatree Gully. It was pure white, free from stains of 

 oxide of iron, and contained no coarsely intermixed foreign 

 matter. 



