BY W. F. PETTERD, C.M.Z.S. O 



tions, and is often much decomposed, when it readily falls 

 to pieces. At Dundas it occurs in limited quantity, but 

 well developed, of a remarkably bright-green colour. 



3. Adularia (Poly silicate of Aluminium and Potassium). 



This is a variety of orthoclase felspar, which is also 

 known as moonstone. It occurs in large crystalline masses 

 porphyritically disseminated in granite. It is usually 

 almost white, but varies to a pale-green colour. 



Locality : Coldstream Rivulet, a tributary of the Hus- 

 kisson River, and also at the Tasman Rivulet, with quartz 

 of various forms (W. R. Bell). 



4. Albite f Poly silicate of Aluminium and Sodium). 



This triclinic soda felspar occurs in solid, irregular, sub- 

 translucent, and compact masses, which are milk-white, 

 at the Heazlewood River, It has also been detected in 

 limited quantity in the mica-solvsbergite of Port Cygnet 

 and at Mt. Lyell. 



o. Almandite (Orthosilicate of Aluminium and Iron). 



The common aluminium-iron garnet. Occurs in small 

 crystals, which are translucent and of fair colouration, at 

 North Mt. Heemskirk ; near George's Bay in association 

 with a dark-green chlorite; at Cape Barren Island 

 embedded in quartz in considerable quantity ; and at 

 other localities. 



6. Aegirite (Metasilicate of Iron and Sodium). 



Also known as acmite. It is a monoclinic soda pyrox- 

 ene corresponding to arfvedsonite in the amphiboles. It is 

 peculiar to the alkaline series of igneous rocks. It occurs in 

 connection with the Port Cygnet complex, and is specially 

 conspicuous in the elaeolit-e-syenite and solvsbergite-por- 

 phyry of that locality, which has become noted amongst 

 petrologists for its interesting series of igneous rocks. 



7. Allophane fHydrated Silicate of Alumina). 



Found at the Savage River as irregular, fairly large 

 masses, coated with a pulverulent white powdery substance 

 of secondary origin. The colour varies from pale-yellow to 

 a much darker shade. The general appearance of the 



