BY W. F. PETTERD, C.M.Z.S. 159 



Abundant as sericite-schist at Mt. Lyell, Mt. Read, and 

 other localities. 



293. Serpentine (Hydrattd Silicate of Magnesia). 



This is in reality a rock rather than a mineral species, 

 resulting from the metamorphism of intrusive igneous 

 rocks, such as the ultra-basic peridotites, which are rich 

 in olivine as a constituent. The mineral olivine is much 

 prone to alteration, and its conversion to serpentine can 

 be distinctly traced in rock sections, and even macroscopic- 

 ally. The eliminated iron from the olivine may be 

 represented as granules of magnetite, or it may be wholly 

 changed into the ferric state, and thence into the minerals 

 hematite and limonite. 



This mineral occurs as a rockmass of considerable 

 extent. Its normal colour is green, of many shades, but 

 almost every known variety of the substance, both in colour 

 and structure, has been obtained in this island in more or 

 less quantity. At the Heazlewood and vicinity it occurs 

 in considerable amount, often containing a perceptible 

 quantity of nickel silicate, which gives it a bright apple- 

 green colour, in which case it approaches that from New 

 Caledonia, which is worked as an ore of nickel. Along 

 the banks of the Heazlewood River and some of the smaller 

 streams much of the serpentine often contains large quan- 

 tities of minute intensely black crystals of chrome spinel, 

 and, more rarely, large amorphous bunches of chromite. 

 Brucite, schiller-spar, and narrow bands of chrysotile also 

 occur with it as accessory minerals. At Anderson's Creek 

 and neighbourhood extensive masses of this rock exist, in 

 many places containing asbestiform chrysotile, and steatite ; 

 north of Trial Harbour it often contains long fibrous asbes- 

 tos, and is connected with an extensive bed of remarkably 

 pure talc ; also occurs at Huskisson River, Clayton Rivu- 

 let, and at the Parson's Hood Mountain. Exposures of 

 serpentine occur on the Styx River and at the head of the 

 Florentine. At the Serpentine Hill near the Renison Bell 

 Tin Mine the serpentine occurs in part transmuted to an 

 intensely black magnetite, the specimens often presenting 

 the attractive appearance of being one-half a beautiful 

 green serpentine, and the balance black magnetite. 



-294. Shale ( Hydrocarbon J. 



Argillaceous shales of a more or less bituminous charac- 

 ter, and of various shades of brown and black, occur at 

 several localities. They are all inflammable to some extent. 

 So far they have not been determined. 



