BY C. A. SUSSMILCH AND H. I. JENSP:N. 183 



composed of four allotriomorphic crystals. Each part abounds in 

 rounded vesicles partly infilled with opal, and contains liquid and 

 gaseous bubbles too. The wliole mass is surrounded by a belt of 

 chalcedony. It is interesting because it must represent either an 

 included crystal-aggregate through which magmatic waters dis- 

 solved their way, and deposited silica during the period of consoli- 

 dation of the rock; or it represents the amygdaloidal infilling of a 

 vesicle by a "eutectic" solution of felspar and hydrous silica, 

 giving a^micrographic intergrowth. In either case it is a good 

 illustration of the influence of pneumatolytic action (cp.X.649). 

 A fair amount of yellowish acmite, in hypidiomorphic needles, is 

 present; and also reddish iron-ores from decomposition. Tridy- 

 niite (V) occurs in minute vesicles. Another isotropic colourless 

 substance present is probably hydrous silica. 



Name : Trachytic Comendite. 



Note : a white lock, with bluish bands and flovv-stiucture, from 

 the same locality is, in handspecimen, studded with large and small 

 vesicles, more or less infilled with white granular minerals. 



C.34. Coarse poiphyritic Solvsbergite. Loc: near The Old 

 Woman. 



Texture: holocrystalline; dosemic; the base is very finegrained 

 and pilotaxitic-stellate. 



Composition: the phenocrysts consist of large felspars (up to 

 -^ inch), smaller segirine-augites, and magnetite. Tlie felspars 

 consist of oligoclase, with multiple twinning and refractive index 

 greater than that of Canada balsam, and the usual typical 

 anorthoclase and microcline-microperthite. The segirine-augite is 

 weakly pleochroic, and extinguishes at 35°. The magnetite is 

 titaniferous, and is accompanied by ilmenite. The base consists 

 of the same minerals, together with secondary limonite. 



Name: Oligoclase-Solvsbergite. 



B. Melanocratic Trachytes, &c. — These rocks are allied to the 

 dark trachytes which occur in the Warrumbungle Mountains (e.g., 

 Timor Ledges, Nandi Mountain, Naman Ledges, kc). 



