598 THE GEOLOGY OF THE WARRUMBUNGLE MOUNTAINS, 



2. Texture : hyalopilitic fabric; uneven in grain. 



3. Composition : the constituents are acicular felspars (albite 

 and anorthoclase), ragged grains of arfvedsonite, and an isotropic 

 base which does not gelatinise and stain. A little magnetite is 

 present, and also decomposition-products such as kaolin, zeolites 

 and brown iron ores. 



4. Name : Hyalopilitic Trachyte. 



W.UO. Loc: Berum Buckle. (Plate xxxi., figs. 9-10). 



1. Handspecimen : a dark grey mottled rock, with large 

 phaneric phenocrysts of tabular felspar. 



2. Texture : holocrystalline, with porphyritic phenocrysts in a 

 very fine, even-grained trachytic base. 



3. Composition : the felspar is of two generations, consisting 

 of phenocrysts of sanidine (or anorthoclase?) and the anorthoclase 

 of the base in minute needles. The usual aggregates of blue 

 hornblende abound, as well as the same mineral in stunted rod- 

 shaped grains. Almost isotropic phenocrysts of regular six-sided, 

 octangular, and four-sided outlines, and of a yellowish colour 

 are present in abundance. They show an anomalous double 

 refraction in the centre, which is partly due to an abundance of 

 inclusions. These phenocrysts consist of altered leucite (pseudo- 

 leucite) and nosean. The inclusions in them are, in part at least, 

 felspar. The felspar phenocrysts also contain throughout inclu- 

 sions of isotropic material, apparently leucite, and of cancrinite, 

 whilst in the outer zone arfvedsonite is occasionally included. 

 The soda-amphibole also tends to crowd round the isotropic- 

 phenocrysts. ^girine-augite occurs interstitiall}^ Accessories 

 are zircon, rutile, etc., as inclusions. 



4. Order of consolidation : 



1. Zircon, Rutile, Apatite 



2. Leucite (now pseudoleucite) , 



3. Sanidine phenocrysts . 



4. Nosean 



5. Blue Amphibole 1 ■ 



6. JEgirine 



7. Anorthoclase base ■ 



