ROCK SPECIMENS FROM CENTRAL AND WESTERN AUSTRALIA. 297 



dark minerals, iron-ores, hornblende and biotite occur in 

 intricate clusters, along with much apatite and a little 

 zircon. The hornblende is almost opaque from dusty 

 magnetite inclusions, is intimately penetrated by biotite 

 and is embraced by compact iron ores, around which and 

 in the bays of which biotite is freely developed. The rock 

 may therefore be interpreted as a hornblende granite, 

 probably belonging to the gneiss series. 



The second rock is labelled " 10 miles E. of Camp 33," 

 i.e., from the east of the Barrow Range. Streich states 

 that the Barrow Range consists of eruptive granite, but 

 mentions the occurrence ten miles east of the range of two 

 small " isolated hills of granulite, which is distinctly 

 stratified with a low angle of dip towards south." Stelzner 

 remarks of one of these specimens that "it resembles so 

 closely the granulite of the Saxon granulite-ellipsis that it 

 could have been found there as well." The present speci- 

 men is distinctly banded in yellow and dark layers, and 

 presents considerable superficial resemblance to the more 

 yellow varieties of jaspers so abundant in the goldfields of 

 Western Australia. It differs from them, however, in a 

 profusion of small red garnets, which when examined with 

 a lens show no sign of crystal faces. In addition the lens 

 reveals an abundance of an elongated well cleaved colour- 

 less mineral with adamantine lustre. 



In section the latter mineral shows prismatic forms, with 

 a, perfect longitudinal cleavage, lias straight extinction, 

 positive elongation, and a birefringence considerably 

 superior to that of quartz (between *015 and *020 according 

 to Levy and Lacroix's colour scale). Basal sections are 

 approximately quadrate in shape, and by their study the 

 mineral is shown to be almost uniaxial and optically posi- 

 tive; the opening of the axial brushes is almost impercep- 

 tible. An examination of tho crushed mineral in liquids of 



