GEOLOGY AND PETROGRAPHY OF THE PROSPECT INTRUSION. 475 



tinous silica produced by the action of the acid showed 

 that analcite and zeolites are most abundant in the same 

 patches, though undetected by optical tests alone. 



Order of Consolidation. The conclusions regarding the 

 order of consolidation of the minerals obtained by a careful 

 study of the slide are best exhibited in the form of a simple 

 diagram, in which the periods of crystallisation of the 

 several minerals are indicated by horizontal lines opposite 

 their names, showing by their length and position the 

 duration and the order of beginning and ending of the 

 periods. Time is represented by horizontal distance from 

 left to right. 



Olivine — 



Magnetite 



Ilmenite 



Biotite 



Apatite 



Augite 



Felspar 



Chemical Composition. By kind permission of Mr. E. P. 

 Pittman, Government Geologist of N.S.W., three analyses 

 were made for us by Mr. J. O. H. Mingaye, Analyst to the 

 Department of Mines, and his assistants. The first of these 

 to be quoted was made from the greater part of the same 

 specimen from which the slide here described was cut. The 

 analysis will be found stated in full in a later section ; it is 

 sufficient here to give the proportions of the essential con- 

 stituents, they are as follows : — 



Si0 2 



46*26 



OaO 



9*18 



A1 2 3 



13*36 



Na 2 



2-27 



Fe 2 3 



2-34 



K 2 



1-23 



FeO 



10*53 



Total H 2 



2-23 



MgO 



8*87 



TiQ 2 



1-78 



