Igneous Rocks of South Western Victoria. 1 1 



surface. An extreme example of a decomposed trachytic rock is 

 aflfoi'ded by "a hill locally called "The Giant Rock" which is, as I 

 stated previously, now little more than a mass of kaolin, with 

 occasional light colored, but still hard bands in the deeper 

 seated portions. Near this, and undoubtedly an outlier of it, a 

 huge stone, many tons in weight, outcrops, and is known to 

 residents as "The Little Rock." The latter is hard, rough, 

 brown in color, and similar both in macroscopic and microscopic 

 characters to the rock from the Mount Eve quarry. The out- 

 lines of the larger crystals of sanidine are still preserved, but 

 they are no longer clear and pellucid, as in less altered rocks. 

 An analysis which I made of a sample from "The Little Rock," 

 srave the followincf result : — 



Total - 98-58 „ 



These two rocks are situated a few miles to the north of 

 Mounts Adam and Eve on the Brit Brit Road. From a quarry 

 not far distant I gathered the fissile, green, fresh-looking rock 

 alluded to in my former paper as emitting a ringing sound when 

 struck with the hammer. No chemical analysis has been made 

 of it, but under the microscope it shfws numerous lath-shaped 

 sanidine crystals, with some tabular ones. 



An excellent illustration of the changes effected in these 

 trachytoid rocks by weathering was afforded some years ago, 

 when an unusually deep as well as extensive quarry was 

 opened near the Coleraine flour mill. Deep down, the rocks are 

 greenish -black and much like a fine grained basalt in appearance, 

 but above the weather line they become almost suddenly light grey 

 or brown, and then might easily be mistaken for a metamorphic 



