x 
(284 W. R. BROWNE. 
Calcite is often found as a central] filling to the zeolite- 
lined cavities in the Prospect intrusion, which is an essexite, 
or more properly perhaps an analcite-dolerite, and the 
author has found, in an albitized facies of the Saddleback 
dolerite outcropping at Port Kembla, calcite filling vesicles 
that are lined with chlorite encrusted by little prisms of 
albite. 
In all these instances the rocks are alkaline in their 
affinities, and the most probable view of the origin of the 
calcite is that it was derived from the residual magmatic 
solutions which had attacked the lime-bearing felspars. 
EXPLANATION OF PLATE. 
Magnification in each case: 145 diameters. 
Fig. 1. Microphotograph of a section of the basalt overlying the 
calcite-bearing type. About the middle of the picture 
are interstices filled with analcite and lined with chlorite. 
At the bottom is an interstitial fibrous-radial zeolite. 
Ordinary light. : 
Fig. 2. Sameas Fig. 1 between crossed nicols. The dark portions 
represent felspar which has been replaced by analcite, 
while in the light-coloured laths the replacing material is 
natrolite(!). ‘The interstices filled with isotropic analcite 
and lined with chlorite show up well. 
Fig. 3. Section of the calcite-bearing basalt, showing the inter- 
stitial disposition of the calcite (white). Most of the 
dark patches are olivine converted into dark red hema- 
tite. Note the fresh augite. Ordinary light. 

