162 THE VICTORIAN NATURALIST. 



abundant biotite occurs. Some of the granites contain two 

 micas or muscovite alone, but pale mica is not common, the mica 

 being usually biotite.) 



Fine-grained patches in the granite are rare. An examination 

 of the larger blocks of granite reveals to some extent the relation 

 of the varieties to one another when in situ in the granite found- 

 ation through which the vent was bored. The porphyritic granite 

 is traversed by non-porphyritic veins of slightly finer texture, 

 which, however, are not separated by a definite line but welded 

 into the general mass. Within the vein an imperfectly banded 

 arrangement of the mica parallel to the junction is seen. At 

 times and towards the middle of the vein the mica is often notice- 

 ably less in quantity : the vein may pass into an aplite. With 

 these veins is seen another feature. In one of them a line of 

 coarser quartz and felspar occurs, cavities on which allow of 

 definite crystallization. Fragments are found also of fine-grained 

 granite, with crystalline nests of quartz and felspar, but I got no 

 such distinct crystals as may be obtained in a similar granite at 

 Learmonth or Addington, some distance to the north. 



Along the side of one of the finer veins is a very coarse band 

 for some distance. It consists of quartz in large patches, felspar 

 with crystal faces developed, and occasional plates of black mica, 

 which sometimes penetrate the felspar. Small cavities allowed 

 free faces on the felspar. The cleavages in twin crystals 

 indicated Manebach twins, and the structure is that figured by 

 Rosenbusch for an intergrowth of microcline and albite. It is a 

 felspar containing potash, but too easily fusible for normal ortho- 

 clase. 



It seems probable that the aplites and part at least of the non- 

 porphyritic granites occurred as veins in the porphyritic granite. 

 The fragments of these rocks are not usually of large size. The 

 granites containing muscovite were not noticed in connection 

 with the other granites in the same block. The highly micaceous 

 black granite was found as a patch in another granitic rock. 



Fragments of decomposed granite also occur, some of which 

 has been completely kaolinized and again indurated, just as occurs 

 where a lava streams flows over decomposed granite. The basalt 

 blocks are either a compact dark variety or one of texture more 

 resembling the common bluestone, sometimes containing minute 

 scales with high lustre, probably hematite or ilmenite. 



There was also noticed, but rarely, a rock, perhaps a somewhat 

 decomposed dolerite. It, however, gelatinized abundantly with 

 strong acid. No olivine was visible — if originally present it 

 would certainly have been already decomposed, and may be 

 represented by limonite, which is present. So that it seems most 

 likely the gelatinization was due to a zeolite. The specimen is 

 still under examination. 



