IBO THE GEOLOGY OF THE CANOBOLAS MOUNTAINS, 



usually idiom Orphic, but slightly corroded, phenocrysts. It is 

 colourless, non-pleochroic, and has an extinction-angle (c' : c) of 

 32°. It is neatly twinned, with (100) as twinning ^ plane. 

 Bx^=C. Optically + . Apparently it is a variety of diopside. 

 Olivine is absent, but ihiienite occurs as small crystals. The 

 base consists of minute, felspar needles, dusty magnetite, and 

 glass. 



Order of consolidation. 



1. Ilmenite 



2. Augite 



3. Felspar phenocrysts 



4. Felspar microlites 



5. Magnetite 



6. Glass 



Name : Augite-Andesite. 



No X. 632. Compact black Forphyritic Andesite. Loc: Hope- 

 toun Waterfall. 



Texture : holocrystalline; porphyritic, hiatal; with microcrys- 

 talline, pilotaxitic base. 



Composition : the chief constituents are felspar of two genera- 

 tions, augite, a little olivine, and titaniferous magnetite. The 

 felspar phenocrysts are beautifully zoned, varying in composition 

 from oligoclase on the rim, to basic andesine or labradorite in the 

 centre. Their other characters are as in .634. In addition 

 they are often extremely corroded, and contain inclusions of augite 

 and chlorite. The microlitic felspar has the properties of albite. 

 Interstitial orthoclase also occurs. Augite does not show as 

 phenocrysts, bnt it is abundant as idiomorphic, faintly purple, 

 grains in the base, changing to chlorite and chloritoid. Titan- 

 iferous magnetite is abundant; a little ilmenite also occurs. 

 Olivine is sparingly present, as corroded phenocrysts, wholly or 

 partly altered to serpentine. 



Name : Olivine- Andesite. 



D. The Basalts. There are two tj^^pes, the common olivine- 

 basalts, and olivine-fayalite-melilite basalts. 



