Vol. 69.] 



PETROLOGY OF THE KALGOORLIE GOLDFIELD. 



to the vertical axis of the crystals (fig. 1). It is often crystallo- 

 graphically continuous with clear green or colourless hornblende ; 

 but the boundary-line is sharp, with no shading of colours as in the 

 Kalgoorlie type. The bulk of the rock consists of clear, strongly- 

 pleochroic, green hornblende in large and small crystals of more 



Fig. 1. — Hornblende-fels, G.S.M. 8140, Mavensthorpe, consisting of 

 original broivn hornblende (shaded, and with oblique roius of 



[lT~ iron-ores), secondary green hornblende (clear), and sphene 

 (dotted). x20. 



compact character than is the case with the simply- uralitized 

 amphibolites ; and it is evident that the rock has attained a higher 

 degree of metamorphism, most probably through contact-alteration. 

 No analyses of pyroxenite-amphibolites from Western Australia 

 are available. 



(g) The Lustre-Mottled Amphibolites ( Hornblende - 

 Dolerite- Amphibolites) . 



These rocks in Kalgoorlie do not form separate intrusions, but 

 occur as local variations of the main band of quartz-dolerite- 

 amphibolite at two or three points on its western side. They may 

 easily be detected in hand-specimens by the lustre-mottling on the 

 cleavage-surfaces of large hornblende-crystals, which range up to 

 15 mm. in their longest diameters. 



