BY H. I. JENSEN. 151 



(x.) Orthophyric Riebeckite Comendite. Loc: Dyke in railway 

 cutting, |-m. N. of Beerburrum Railway Station (Plate xiv. 

 fig.22). 

 This is a beautiful orthophj'ric riebeckite rock like that from 



Tibrogargan (vii.). 



(xi.) Orthophyric JEgirine Comendite (?). Loc. : Mt. Ewin. 



This is a noncrystalline, very fine-grained orthophyric rock, 

 with a cryptocr} r stalline base. The recognisable crystals consist 

 of sanidines, regirine, and a little blue soda-amphibole. 



(xii.) Porphyritic-Quartz-Riebeckite Comendite (?). Loc: Mt. 

 Cooee, near Mt. Tibrogargan. 

 This rock has large, highly corroded, quartz phenocrysts lying 

 in an orthophyric mass. The grain-size of the main mass is fine; 

 the minerals present, in addition to quartz, are isometric felspar 

 crystals (sanidin-anorthoclase), soda amphiboles behaving like 

 riebeckite and cossyrite, a very small amount of highly corroded 

 biotite, and the cryptocrystalline interstitial mass. Both the 

 quartz and the biotite are probably allogenic minerals snatched 

 up from the country rock when the magma rose to the surface. 



(xiii.) Orthophyric Pantellarite. Loc: Mt. Ngun-Ngun (Plate 

 xiv. fig. 2 3). 

 This is a holocrystalline, porphyritic, orthophyric rock, with a 

 fine-grained microcrystalline to cryptocrystalline base. The 

 constituents are sanidine, anorthoclase, arfvedsonite, riebeckite, 

 and cossyrite. The last-mentioned mineral is found chiefly 

 enveloped by arfvedsonite or intergrown with it. The analysis of 

 this rock (Anal.iii. p.168) shows it to be a pantellarite; and the 

 magmatic name (Norm. hi.) is liparose. Its titanium-content is 

 high. 



(xiv.) iEgirine-Trachyte, Loc: Round Mountain, near Cabool- 

 ture (Plate xvi. fig. 36). 

 This is a fine-grained, holocrystalline, microporphyritic rock, 

 with a pilotaxitic fabric. The constituents are sanidine, segirine, 

 a little deep blue amphibole (probably riebeckite), and a green 

 mineral having a crystalline form and cleavage, occurring in rods, 

 but behaving optically like glass, being isotropic. 



