98 GEOLOGY OF MT. FLIN'DERS ANI> FASSIFERN DISTRICTS, q., 



is fairly plentiful, and appears to be secondary after cubes of 

 ma<'netite. Chloritic and serpentinous decomposition-products 

 occur more sparingly, and a little interstitial fluorite seems present. 



The peculiar texture and composition of this rock indicate that 

 it consolidated under tlie influence of pneumatolj^tic action. It 

 forms a dyke in trachyte-tuffs. 



Name : Panidiomorpliic Soda-Trach3^te. 



ChemicalC omposition : 

 Per cent. Mol. 

 SiO.^ 65-09 1-085 Norm: 



0-141 Quartz .... 

 3 "2 1 0-020 Orthoclase. 



FeO 0-13 0-001 Albite 



MgO 0-10 0-00-2 Acmite 



CaO .. 1-18 0-021 Hyperstheiie 



Na.jO 7-2(3 0-llS Haematite.,.. 



K.2O 3-24 0-034 Titanite 



H9O 2-42 Ilmenite 



TiO., 2-50 0-031 Water 



99 56 



Chemical classification : Class i., Order 5, Rang 1, Subrang 4. 

 Magmatic name : Umptekose. 



Note. — This rock will be further investigated when more and 

 better material are obtained. The unknown mineral appears to be 



quite a new one. 



3. The Andesites. 



F1.23. Loc: near Hotel Reserve, Little Liverpool Range. 



Dark vesicular andesite containing white, decomposing plagio- 

 clase phenocrysts which fall out in grinding the section. 



Texture : holocrystalline, perhaps hypocrystalline. Fine- 

 grained, with medium to coarse phenocrysts. Serial porphyritic, 

 dopatic. Fabric, pilotaxitic intersertal. 



Composition : the felspar phenocrysts consist of andesine; 

 felspar forms the main constituent of the rock. The smaller 

 crystals are mostly andesine, but some are distinctly oligoclase 

 and albite. The andesine and oligoclase exhibit Carlsbad and 

 albite twinning. Habit, tabular and prismatic, lath-shaped 



