PROCEEDINGS OF SECTION C. 451 



unaltered isotropic microlite enclosed in a meshwork of the same 

 mineral, more or less cloudy, and evidently altered somewhat — probably, 

 judging from the analysis, by absorption of water. Throughout the 

 section are tiny pinpoints of black manganotantalite. 



A fragment of a pale pinkish color, which on sectioning was found 

 to be practically free from included tantalite, was chosen for analysis. 

 It has, unfortunately, not been found possible so far to complete this 

 analysis, but the following are the results obtained up to the present : — 



Tantalum pentoxide \ 77.1 r 

 Niobium pentoxide 1 



Lime 13-46 



Magnesia -42 



Iron protoxide 3-64 



Manganese protoxide -GO 



Potash -20 



Soda 1-66 



Water on ignition 1-06 



Water at 100° -22 



98-42 



Specific gravity 5-422 



The analysis proves this mineral to be essentially a pyro-tantalate 

 of lime of the form CajTajO;, part of the lime being replaced by alkalis, 

 iron oxide, &c. Like most tantalum minerals, it probably carries a 

 little tin oxide, which has not been estimated. 



Of interest in this connection are a few small pebbles received on 

 another occasion from Wodgina. One consists of a large core of a 

 dark-colored tantalate, completely surrounding which is a layer about 

 five millimetres thick of pale microHte similar to that described above, 

 covered in its turn again by a very thin coating of black tantalite. A 

 second pebble is similar, whilst two others are wholly composed of a 

 greyish-black opaque, and apparently homogeneous mineral. One of 

 these latter pebbles, weighing 18grms., was broken in half, and one 

 half analysed, with the following results : — 



Tantalum pentoxide 73-82 



Niobium pentoxide 6-44 



Tin dioxide -72 



Titanium dioxide -54 



Iron protoxide 8-42 



Manganese protoxide 1-39 



Lime 7-78 



]\Iagnesia -62 



Cerium and yttrium oxides Nil 



99-73 



Specific gravity 6-04 



Without further investigation it is impossible to say whether this 

 is only a very intimate intergrowth of microlite and tantalite, or, as 

 I am inclined to think, a new subspecies of tantalite, in which lime to 



