50 E. 0. Teale: 



Ihe linear arrangement of these outcrops suggests the occurrence 

 of a shear or fracture zone along this line, which favoured at recur- 

 ring intervals the access of silicifying solutions. The jasper which 

 is a definite alteration product of the diabase is distinct in character 

 from the black bedded cherts, which are altered stratified deposits. 



(b) The Siliceous-Carbonate Rocks. 



These rocks form a very striking and characteristic alteration 

 product in the diabase area, and are identical in character with 

 similar rocks occurring in Heathcote. In appearance the rock has 

 a somewhat schistose structure due to fine and contorted banding. 

 (Sec. 51.) It has a prevailing brown colour, with greenish streaks 

 due to a substance allied to selwynite or green chalcedony, which 

 .also occurs in lenticles and patches. Numerous sections examined 

 by Professor Skeats from Heathcote indicate that this was origin- 

 ally a diabase or diabase tuff which has suffered alteration in two 

 stages. First it was subjected to a carbonating solution, which 

 produced a mixture of iron, lime and magnesian carbonates, and, 

 later, siliica bearing solutions invaded the rock, replacing in part 

 the original carbonate. 



Four separate outcrops of this rock have been noted. One is in 

 i:he bed of the Howqua, at tlie pack horse bridge, near Fry's — (specs. 

 51-54); a second about a mile farther down the river, associated 

 with the smaller diabase area ; the third is on the track to Cameron's 

 Creek — (Spec. 44)— about a quarter of a mile south oa Lick Hole 

 Creek; and the fourth is about half mile to the south-west of this 

 «pot — (Spec. 113). The two lastnamed occurrences are in close 

 proximity to a serpentine outcrop, and the first is on a fracture 

 line leading to another serpentine area. It may be, therefore, that 

 the concentration of carbonates in one place may be casually con- 

 nected with mineral redistribution, which took place during ser- 

 pent! nization. 



C. The Talc Rocks. 



These rocks vary from massive talc rock and talc schist, un- 

 ■doubtedly altered diabase to talcose sediments, which may be 

 altered tuff beds. The latter will be referred to again, when deal- 

 ing with the lower Palaeozoic sediments. Talc rock is abundant at 

 the north-western end of the diabase area, in the valley of Stock- 

 yard Creek, and its greasy nature adds to the difficulty for horse 

 ■traffic on the steep graded track to the Howqua from Timbertop 



