31 



to the base. Basal sections give unequal octagonal forms i 

 sometimes idiomorphic, sometimes allotriomorphic, in relation 

 to the felspar. It is fairly abundant. Biotite is represented 

 by green chloritic pseudomorphs, and a few outlines are 

 those of hornblende. 



5. Lheezolite. 

 Sp. Or. 2-93. 



This is another rock belonging to the varied peridotites 

 which are found at the Heazlewood. The mineral com- 

 bination is olivine + enstatite + monoclinic pyroxene, and it 

 has been called Lherzolite after the lake Lherz in the 

 Pyrenees. Of these three minerals, olivine greatly pre- 

 ponderates, and it is not difficult to imagine the pyroxene 

 failing entirely, and a dunite or purely olivine rock to result. 

 The rhombic pyroxene is the only other constituent present 

 in any quantity, for there is very little monoclinic pyroxene 

 indeed. The structure is hypidiomorphic - granular, and 

 both pyroxenes and olivine are reticulated with serpentine 

 meshes. Olivine grains are often enclosed in the enstatite, 

 and there is no approach in the latter to hypersthene. The 

 augite resembles the diallagic variety rather than 

 diopside, and neither pyroxene is serpentinised to the same 

 extent as the olivine. There is some chlorite in the rock, 

 besides grains of magnetite (?) and wisps and meshes of 

 titaniferous iron, and its alteration product, leucoxene. 



This is a close textured rock, without any striking peculi- 

 arity. It is greyish green in colour throughout in the solid 

 portions, but where slight fractures occur, a dark green, 

 almost black, tiut prevails, with a slight glaze, otherwise the 

 mass is dull in general appearance. It occurs in the form 

 of an intrusive dyke of restricted dimensions at the 10-Mile, 

 Waratah-Corinna Road. 



6. Websteeite. 

 Sp. Or. 2-82. 



Mineral Composition, Diallage and Enstatite. 



Websterite, as established by O. H. Williams, is a pyroxe- 

 nite, consisting of monoclinic and rhombic pyroxenes. These 

 are the constituents of the Heazlewood rock, the augite being 

 predominant. In parts it consists of long prismatic forms, 

 which have not been attacked by serpentinising agencies : else- 

 where it seems to have formed somewhat larger diallagic 

 plates, which are nearly wholly replaced by serpentine. It is 

 difficult to determine precisely whether olivine in small 

 quantity was present, as the serpentinisation of the rock has 

 obscured its original facies. The enstatite is not abundant,, 

 and it is mostly enclosed in and intergrown with the diallage. 



