BY W. K. BENSON. 703 



teschenitic characters, and their relation to the basanites is quite 

 obvious. 



The rock, N.T., 163, described in the Note as forming a small 

 neck, one mile from Goonoo Goonoo, is of quite similar character, 

 and less decomposed. Analcite, not previously recorded, has since 

 been found, and sanidine and orthoclase are present in small 

 amount. Apatite and abundant ilmenite also occur, the latter often 

 surrounded by tiny mica-plates, perhaps the result of the inter- 

 action of the analcite and ilmenite. The augite shows hourglass- 

 structure, and is free from inclusions. Small grains of the second 

 generation are also present. Olivine forms large, fresh crystals. 

 It is possibly better to regard this rock as a teschenite-dolerite 

 than as an essexite. There seems little reason to doubt the pri- 

 mary nature of the analcite. 



In the Preliminary Note on these rocks, their extension from Mt. 

 Warrawalong to Nundle was shown, but a large increase in this 

 area can now be indicated. The Prospect essexite near Sydney, 

 recently described by Jevons, Jensen, Siissmilch, and Taylor(46) 

 is, in its nature, related to the essexitic or teschenitic dolerites of 

 Nundle. The analcite-dolerites and essexites described by Jensen, 

 in the Nandewar Mountains [N., 17; N., 28; and N., 57] ; (9, pp. 

 880-883), are clearly of this type, and are found in sills; while the 

 rock of Delungra Peak, near Gragin, 20 miles east of Warialda, 

 described by Mr. Came and Mr. Card (27), is also one of this 

 series, and is probably similar to that of Mt. Warrawalong in its 

 manner of occurrence. I have also received, from Mr. R. A. 

 Wearne, a specimen from Mt. Melora, .near Ipswich, which has 

 proved to be a most beautiful example of teschenite, showing 

 partial replacement of the plagioclases by analcite and natrolite 

 There can be no doubt that it belongs to this intrusive series, and 

 is well worth further investigation. This emphasises the remarks, 

 made formerly, of the close association of these with the Tertiary 

 basalts, and the manner in which they reflect the varying degree 

 of alkalinity of those basalts. The extent now proved for these 

 rocks is nearly 500 miles (Sydney to Ipswich). 



