596 ALKALINE PETROGRAPHICAL PROVINCE OF E. AUSTRALIA, 



patches which have been variously termed poecilitic, ophitic, 

 feathery, mossy, or dendritic. 



An analysis of the Bowral arfvedsonite has been made by Mr. 

 D, Mawson, and this type of soda-amphibole appears the most 

 abundant in all the alkaline areas which I have studied. 



Perfect crystals are rarely met with; those described by Mr. 

 Mawson in the Gib syenite-pegmatite or bowralite are unique 

 instances. 



When barkevicite (the more calcic species) becomes dominant 

 there is a stronger tendency to idiomorphism. 



4. Certain minerals of the group rich in rare earths are usually 

 present. The exact species is not always the same. The com- 

 monest is laavenite, but wohlerite, eudialite, rinkite (?), mosand- 

 rite C?), <fcc, also occur. These minerals are frequently very rich 

 in Ti0 2 , a substance which must also be present in the femic 

 minerals. 



5. As other important and frequent accessories one might 

 mention zircon, magnetite, ilmenite, and rutile (occasionally 

 pseudobrookite). Apatite is rarely present. 



6. In the more basic rocks plagioclase felspars occur with the 

 anorthoclase, and occasionally felspathoid minerals enter into 

 the composition, such as pseudoleucite, nosean, sodalite, nephe- 

 line, &c. 



On the whole the character of the felspar of our alkaline rocks 

 is the most constant feature. Everything considered, there can 

 be no doubt that a close genetic resemblance exists between the 

 mineral contents of all the groups of alkaline rocks in Eastern 

 Australia. 



E. Order of Consolidation. 



In all the Australian alkaline rocks which I have so far 

 investigated, the same order of consolidation of minerals is main- 

 tained for each rock-type. The sequence is generally one of 

 decreasing basicity. 



In the trachytes, magnetite, when present, was the first 

 mineral to form, and it has always been strongly corroded and 



