BY H. I. JENSEN. 117 



sists of decomposing crystals of orthoclase and biotite, and quartz 

 grains. Many of the grains are encrusted with manganese 

 oxide, probably derived from the decomposition of a hornblendic 

 mineral. Through decomposition this granite has taken on a 

 stratified appearance which makes it very like sandstone. 



Epi-Diorite. Loc: D'Aguilar Ra., near Mt. Crossby, near Tpswich. 

 (Plate xi., fig. 4). 



i. This specimen was collected and given to me by Mr. H. L. 

 Thompson. Colour greenish, due to a mixture of light green, 

 greyish-green and yellowish-green plagioclase grains, with green- 

 ish-black hornblende crystals. It is phanerocrystalline and 

 coarse-grained. 



ii. (1) Texture: (a noncrystalline; (b) even-grained and coarse, 

 but the large grains are made up of many small grains of medium 

 size ; (c) hypidiomorphic granular, inclining to panidiomorphic 

 granular. 



(2) Constituents (in order of decreasing abundance) — (a) labro- 

 dorite, (b) actinolite, (c) uralite, (d) quartz (subordinate in 

 amount), (e) brownish ilmenite, (f) apatite. 



(3) The plagioclase ranges in basicity from Ab x An x to Ab 3 An 4 , 

 and gives sericite as a decomposition product. The uralite is 

 closely allied to actinolite, into which it appears to be altering. 

 Both these minerals are secondary after some pyroxene. The 

 other minerals are mere accessories. 



(4) Order of consolidation normal. 



(5) Nomenclature. — This rock was originally a quartz gabbro 

 which, by alteration of augite into hornblende, has become a 

 quartz-epidiorite. 



(6) Remarks. — Very many interesting gabbros occur in this 

 part of the DAguilar Range. They are associated with serpen- 

 tines and peridotites. Manganese deposits occur in the neigh- 

 bourhood of Mt. Crossby. 



Graphic Granite. Loc: Woodford. (Plate xi., fig. 5). 



My section was cut from a specimen collected by Mr. J. M. 

 Newman, B.E., and presented by him to the University Geology 

 Dept. 



