Mocks of the Hoiuqua River. 45^ 



In this rock mucU recrystallisation under pressure has occurred. 

 Most of the augite has recrystallized as fibrous secondary horn- 

 blende, Avith light to dark green pleochroism, and extinction angles - 

 ranging from 11° to 21°. The felspar has recrystallized to water 

 clear secondary felspar, with enclosures of secondary hornblende 

 needles. Ilnienite in large skeleton rhombohedra altered to leuco- 

 xene, is fairly abundant. Some interstitial secondary calcite is 

 present. The extensive recrystaJlization of the rock is no doubt 

 referable to its occurrence in a crushed zone, south of Fry's, and 

 it resembles some of the recrystallized diabases of Heathcote and' 

 Mt. William, near Lancefield, but is hardly so altered as the epidio- 

 rites of Ceres, near Geelong, since some relic structures in the form' 

 of original augite and felspar are still noticeable. 



No. 18. — Diabase, south-east of No. 17. 



Pl diabase which has suffered fairly complete recrystallization to- 

 fibrous hornblende, and secondary water clear felspar. In the 

 process a considerable amount of granular and dusty magnetite has 

 separated out. 



No. 22. — From main diabase mass. Lick Hole Creek, and east 

 of isolated crushed diabase mass. A relatively coarse-grained type 

 with no signs of recrystallization under pressure. Coarse plates 

 of augite and cloudy felspar form the bulk of the rock, with 

 chlorite and clear felspar as secondarj^ products. 



No. 25. — Soda rich diabase (analysed), Lick Hole Creek, one 

 mile north of the Governor, and near the south-east end of the 

 main diabase mass. (Micro. Photo., Plate I., Fig. 1.) 



About 2-3rds of the rock consists of felspar in large and small' 

 prismatic, quadrate or irregular crystals. Simply twinned and 

 untwinned crystals are abundant, and some show lamellar twin- 

 ning. The low refractive index, positive sign, and biaxial figure- 

 show that albite or albite-oligoclase predominates. All the felspars, 

 are clear, and some contain secondary hornblende and chlorite, 

 suggesting recrystallization. Some original augite remains, but 

 much is altered, either to normal hornblende or green pleochroic 

 fibrous actinolite. Sphene, epidote and zoisite occur in granules. 

 Brown clusters of radiating biotite crystals occur, and some calcite, 

 a little quartz, and a few elongated prisms of apatite are present. 

 The high albite content of the rock is confirmed by the chemical 

 analysis, but it is difficult to reconcile the relative abundance of 

 ferro-magnesian minerals with the strikingly low magnesia content- 

 recorded in the analysis. 



