265 



outcrop from which these specimens were derived proved the 

 irock to be a very coarse-grained igneons injection, perhaps 

 best described as a gabbro-pegmatite. It outcrops in the 

 Pre-Cambrian area on the creek about a mile below Mount 

 ! Gee. The sphene crystals are of a clove-brown colour, and 

 some were discovered that weighed several pounds. They are 

 embedded in a coarse uralitized-diopside. The formation 

 recalls the "yatalite" of Benson, from the Pre-Cambrian area 

 near Adelaide. 



10. Dawidite. — In a preliminary notice ( 2 ) concerning 

 radio-active minerals from the Radium Hill lode, near Olary, 

 the name davidite was sug-o-ested for one of them. Since that 

 date mining operations have opened up the lode and exposed 

 additional features of interest. A special contribution on the 

 subject will be forthcoming shortly, but in the meantime 

 further reference to the association and identity of davidite 

 is due. The davidite iri its pure form is but rarely met with 

 in the lode. It is in the form of streaks, grains, and crystals 

 embedded in the other filling. The latter is chiefly radio- 

 active ilmenite of a non-homogeneous character. In places 

 grains and patches of pure rutile appear. Occasionally in the 

 more massive portions of the lode stringers of quartz, centrally 

 disposed, make their appearance. Embedded in such quartz 

 nice cuboid crystals of davidite are to be met with. In thin 

 sections, under the microscope, these crystals appear homo- 

 geneous, and there is no evidence that they are a mechanical 

 mixture of mineral ingredients. An analysis by Dr. W. T. 

 Cooke of some of this material is published elsewhere. <. 3) The 

 radio-active ilmenite forming the general lode-filling becomes 

 blacker and duller in the deeper zones, and at the same time 

 is more highly radio-active. The principal change is that of 

 decrease of titanium and increase in iron and uranium. In 

 certain pockets and apophyses the filling is mainly coarse, 

 intensely black biotite, ,4) through which the radio-active 

 mineral is distributed as nodules. These latter commonly 

 contain 8 per cent. TJ 2 3 . The mineral composing these 

 nodules weathers comparatively readily, and, as met with, is 

 often in the state of brown, earthy aggregates. On the spoil 

 heap, where the micaceous gangue has been dumped at the 

 mouth of the shaft, a growth of carnotite is to be observed 

 developed on the flakes of black biotite subsequently to 

 reaching the surface. The biotite thus becomes, in the course 



(2) Vide Trans, and Proe. Roy. Soc., S. Aus., 1906. 



(3) Vide Trans, and Proe. Pot. Soc, S. Aus., present volume,' 

 p. 267. 



(4) Vide Report by R. E. Stanley: Trans, and Proe. Roy. Soc 

 :S. Aus., present volume, p. 26&. 



