94 GEOLOGY OF MT. FLINDERS AND FASSIFERN DISTRICTS, Q., 



Soil : this rock yields a good soil, rich in magnetite which 

 collects as black sand in the streamlets after rain. 



F1.24. Loc: Governor's Rock, top of Little Liverpool Range. 



Handspecimen : somewhat decomposed, reddish, trachytic 

 rock. 



Texture : even-grained; micro- to cryptocrj^stalline with pilo- 

 taxitic fabric. 



Composition : the felspars are anorthoclase and oligoclase in 

 equant and acicular microlites. The base is decomposed and 

 kaolinised. The original soda-amphibole is decomposed to red 

 iron-ore, which is left in ophitic (mossy) aggregates. 



Name : Oligoclase-Trachyte. 



Soil : sandy and poor. This formation covers a considerable 

 area on the range. 



Fl. 19. Loc: various places south of Engelsburg. 



Porous (miarolitic) coarse-grained grey rock in handspecimen, 

 not unlike some specimens of Gib syenite-pegmatite (bowralite). 

 The rock, on account of its porous nature, is very ditficult to 

 section. The slice examined was greatly broken up, yet suflS.cient 

 portions retained cohesion so as to show structure and composition. 



Texture — Crystallinity: holocrystalline. Granularity: medium, 

 uneven, serial-porphyritic, persemic. Fabric : hypidiomorphic- 

 granular. 



It appears like a coarse-grained rock, but in the interstices, 

 between the idiomorphic large crystals, are smaller crystals of 

 hypidiomorphic or allotriomorphic outlines. 



Composition : the large crystals forming the main bulk of the 

 rock are idiomorphic, and belong to two felspar-species, (I) oligo- 

 clase known by its refractive index slightly above that of canada 

 balsam, and double refraction slightly higher than orthoclase; 

 and (2) anorthoclase. 



The oligoclase exhibits carlsbad, albite and baveho twinning; 

 and also beautiful mechanical and optical zoning, the former due 

 to bands of dusty material and minute sagenitic rutile needles, 

 arranged parallel to the outlines of the crystals; the latter kind 



