164 VOLCANIC AREA OP EAST MORETON, ETC., DISTRICTS, Q., 



is common to many of the highly ferriferous basalts of the 

 district, e.g., the Buderim, Blackall Range, and Woondum 

 basalts. 



The first generation of augite was low in iron and contained 

 no ferric iron. The second generation must have been rich in 

 ferric iron, being yellowish. The glass, probably, is of the 

 augite-acmite composition. 



(e) Tuffs. 



The country lying between Nambour and Cooroy, the Blackall 

 Range, and Nindherry, is very rich in volcanic tuffs and breccias. 

 Tuffaceous and brecciated rocks were represented in two-thirds 

 of the railway cuttings between Nambour and Yandina; and, in 

 addition, all the flat country lying between Yandina and 

 Eumundi, as well as a great portion of the Eumundi Ranges, 

 between Eumundi and Cooroy, is composed of tuffs and 

 breccias. Mt. Eerwah is partly built up of tuffs which seem to 

 be of a trachytic composition; while in Yanganuien Valley 

 andesitic tuffs and breccias are met with. Most of the tuffs of 

 the Yandina-Nambour railway cuttings are of a light colour, 

 greyish-white to pink, and have the appearance of being com- 

 posed chiefly of felspar. Probably they are trachytic inclusions 

 of boulders, and smaller lumps of sandstone are met with in these 

 tuffs. Owing to the degree of decomposition, as well as to the 

 friable nature of these rocks, no attempt has been made to 

 section more than the one described below. 



Sp. No. 162. Loc: Eumundi - Kenil worth Road, \ mile from 

 Eumundi. 



This specimen is light greenish in colour, otherwise, not unlike 

 a trachyte. A few angular fragments may be seen in it with 

 the naked eye and demonstrate its clastic origin. 



Microscopic examination. — Texture: This rock is hemi- 

 crystalline, porphyritic with an aphanitic base, which has a 

 tuffaceous structure. 



Constituents. — The rock is wholly composed of felspar and 

 decomposition products after felspar, e.g., kaolin. A little 

 hematite and chlorite appear also to be present. The original 



