579 



THE MINERALS AND GENESIS OF THE VEINS AND 



SOHLIEREN TRAVERSING THE ^GIRINE- 



SYENITE IN THE BOWRAL QUARRIES. 



By D. Mawson, B.E., B.Sc, Lecturer in Mineralogy and 

 Petrology at the University of Adelaide. 



(Plates xlix.-li.) 



Contents. 



page 



i. The Parent Intrusive Mass of yEgirine-Syenite ... 580 



ii. Descriptions of the Veins ... ... ... ... ... ... 582 



(a) Bitumen veins. 



(b) Simple pegmatite veins. 



1. Those of small dimensions. 



2. Those of larger dimensions. 



(c) Veins exhibiting well marked flow structure and of finer grain 



(related to the aplites). 

 iii. The Minerals ... ... ... ... ... ... ... ... 587 



(a) Mgirine — Results of analysis — Notes on the analysis— Discus- 



sion of the formula — Petrological features — Alteration and 

 decomposition products. 



(b) Arfvedsonite — Morphological and optical characters — Result of 



analysis — Notes on the analysis — Development of a formula 

 — Comparison with former analyses — Decomposition products 

 — Special features. 



(c) Felspar. 



(d) Accessory minerals — Quartz— l'erofskite(?) — Ilmenite — Zircon 



— Apatite, 

 (e) Secondary mineral* — Bitumen — Chalcedony — Quartz — Siderite 

 — Iron and manganese oxides — Analcite — Fluor — Titanite — 

 Leucoxene. 



iv. Summary and CoNci.isioxs ... ... ... ... 602 



Explanation of the Plates ... ... ... ... ... ... ... 607 



