THE MINERALS OF NEW SOUTH WALES. 209 



It also occurs as a white powdery mineral in a soft grey-coloured 

 amygdaloidal trachytic rock at Myalla. This mineral may at once 

 be recognized from its readiness to undergo decomposition. 



Mesotype. 



Chem. comp. : Hydrous silicate of alumina and soda. Found in 

 amygdaloidal basalt. Locality (1) 



Scolezite. 



Same chem. comp. as the above. Rhombic system. This 

 mineral is found with cylindrical masses of bitter spar in a 

 basalt, Emu Creek, New England. It is distinguished by curling 

 up like a worm before the blowpipe, — hence the name, from 

 o-KU)\r]$, a worm. 



Analcime, or Cubical Zeolite. 



Chem. comp. : Hydrous silicate of alumina and soda. Cubical 

 system. Occurs at Invereli. 



Chabasite. 



Chem. comp. : Hydrous silicate of alumina, lime, and potash ; 

 Hexagonal system : commonly assumes rhombohedral forms. 

 This is perhaps the most abundant of the New South Wales 

 zeolites, and the crystals are often very well developed. It 

 occurs in basalt with delessite at Musclebrook. And in well- 

 formed rhombohedra in trachyte on the Lachlan River ; also in an 

 amygdaloidal basalt at Reedy Creek, Sutton Forest ; with calcite 

 in a similar rock at Coroo. It also occurs in the cavities of a puce- 

 coloured rock at Fountain Head in simple rhombohedral crystals 

 of a wax-yellow colour, and is associated with a bright orange- 

 coloured powdery mineral and a grey-green steatitic substance ; 

 the matrix can be readily cut with a knife, and leaves a shiny 

 streak. 



It is also reported from the Talbragar and Abercrombie Rivers, 

 and is present in the basalt of the Illawarra district. 



Herschelite. 



This is probably only a variety of gmelinite, one of the chabasite 

 group, and occurs with calcite and analcime, crystallized in double 

 hexagonal pyramids at Invereli. 



Prehnite. 



Chemical Composition : Hydrous silicate of alumina and lime. 

 Rhombic system. Occurs at Emu Creek, New England, of a green 

 colour ; and in association with orthoclase felspar and copper ores, 

 at Reedy Creek, Molong. 



