BY W. F. PETTERD, CM.Z.S. 145 



(1) Rhomhic Pyroxenes. 



Enstatite, with kss than 5 per cent, of FeO. 

 Bronzite, with 5 to 14 per cent, of Fe 0. 

 Hypersthene, with above 14 per cent, of Fe O. 



The most highly ferriferous is termed amblystegite, and 

 the fibrous variety is known as bastite. 



(2) Monodinic Pyroxenes. 



Augite, dark-coloured variety, 



Diallage (this alters to schiller-spar), and 



Various green to white varieties. 



The first are abundant in various rocks of igneous origin, 

 such as diorites, porphyrites, andesites, and some perido- 

 tites. The last occur also in plutonic and volcanic rocks, 

 especially those of a basic nature — basalts, gabbros, ande- 

 sites, &c. 



268. Pyrophyllite (Hydrated Silicate of Aluminium). 



This mineral is very plentiful at the Mt. Bischoff Mine 

 in close association with various forms of pyrites and cas- 

 siterite. It forms radiating aggregations of thin scales, 

 which have a yellowish-white colour and glimmering lustre. 

 Before the blowpipe the substance exfoliates and swells to 

 a large size, and with nitrate of cobalt solution it strongly 

 reacts for aluminium. At the Shepherd and Murphy 

 Mine, Bell Mount, it is fairly common in small radiating 

 patches, which are often implanted on quartz, and may 

 contain imbedded crystals of cassiterite. At North Heems- 

 kirk it is also plentiful under the same conditions, but it 

 is usually at this locality of a paler, almost white, tint. 



Mr. R. Sticht has very kindly forwarded me several 

 examples of what is undoubtedly pyrophyllite from the 

 Mt. Lyell district, as well as one from a locality a few 

 miles north of the Emu Bay Railway Company's bridge 

 crossing the Pieman River. That from the North Mt. 

 Lyell Mine is a massive form, with a micaceous scaly struc- 

 ture; it has a glimmering lustre, and is of a pale-greensh 

 colour. 



The analysis gave the following result: — 



Per cent. 



Silica = 62-3 



Alumina = 31-4 



Ignition loss, i.e., 



combined water = 6*02 



99-72 



