162 THE MINERALS OF TASMANIA. 



vein at the North Pieman ; in small quantity at the old 

 Hampshire Silver Mine ; in company with other metallic 

 minerals at the abandoned Penguin Silver Mine; Castle 

 Forbes Bay (Johnston, " Geology of Tasmania ") ; and at 

 North Mt. Heemskirk. 



301. Smectite (Hydrous Basic Aluminium Silicate). 



This is an extremely soft substance, with a metallic, 

 almost silvery, sheen. It easily separates into folise of 

 remarkable tenuity. It is obtained in masses of almost 

 gelatinous softness, but soon becomes harder by loss of 

 hygroscopic moisture. 



It occurs at the North Mt. Lyell Mine and at North 

 Mt. Heemskirk. 



Kespecting this substance, Mr. Sticht remarks: — "The 

 composition of this substance is not in Dana, the analyses 

 given in the work being rather different, to such an extent 

 that it is rather difficult to classify it as any varieties of 

 the obscure substances mentioned in the book. Originally 

 it was very gelatinous or glutinous, i.e., thinner than gum, 

 there being also evidently a high percentage of water in it. 

 The humidity was gi-eat enough to allow it to be very 

 easily moulded with the fingers, like melted wax, although 

 it was much more transparent than that substance. It 

 had a yellowish-green colour while moist, and an acid, 

 astringent taste, which it still retains, and there was also 

 some copper in the moist portion. The water-soluble part 

 was removed before analysis, and all mechanically-con- 

 tained foreign substances, like bits of quartz, &c., were 

 likewise removed. The analysis therefore represents an 

 attempt t'o get at the composition of the pure stuff itself. 

 It was as follows : — - 



99-8 



The ignition loss is considered to be combined water. The 

 loss found in drying before analysis at 100° C. was 13'10 

 per cent. Probably the presence of potash is exceptional. 

 It is doubtless a decomposition product under the influ- 

 ence of sulphuric acid or sulphate solutions. It is not very 



