280 W. R. BROWNE. 
with analcite or fibrous-radial natrolite, and partly with 
fibrous chlorite, often enclosing a core of analcite; rarely 
is calcite found. The vesicles of the rock are filled with 
analcite, natrolite or calcite, and are often lined with 
chlorite. (Plate XV, figs. 1 and 2.) 
The calcite-rich rock is massive, and consists mostly of 
plagioclase, with augite, calcite, olivine and ilmenite in 
that order of relative abundance. The plagioclase, which 
must constitute more than half the rock by volume, is in 
laths occasionally attaining a length of 2 mm., and of a 
composition at least as basic as Ab4gAns;. It is much. 
affected by alteration, the alteration products being irregu- 
larly distributed and often somewhat decomposed. In 
some places they are evidently albite, in others analcite, 
but elsewhere a colourless mineral of distinctly lower 
refraction but stronger birefringence than the felspar: this 
may be natrolite. 
Augite is in small prisms and granules of a yellowish- 
green colour, with observed extinction angles up to 40°, 
and without noticeable pleochroism. To a slight extent it 
is moulded by the felspar, but mostly it is interstitial and 
sometimes slightly ophitic towards the latter Olivine has 
been converted almost completely into brownish-red trans- 
lucent pleochroic hematite, often partly rimmed by an 
opaque margin of the same, the original olivine having 
evidently been a highly ferriferous variety. The primary 
iron ore is ilmenite, with skeletal habit. 
The interstices between the felspar laths may be filled 
with augite and ilmenite, and sometimes with a green 
chlorite-like substance, but for the greater part there is 
a mesostasis of calcite, which makes up about 13 per cent. 
by weight,’ or 14 per cent. by volume, of the whole rock. 



1 Based on a determination of CO, kindly made by Mr. G. J. Burrows, 
B.Sc., of the Department of Chemistry, University of Sydney. 

