90 THE MINERALS OF TASMANIA. 



by north-west course for a distance of about 7 miles, and 

 it is remarkable that on either side of this strike, although 

 in close proximity, other small lagoons occur which are 

 devoid of any appreciable quality. This may be owing to 

 the non-saline lakelets having outlets, by which overflow 

 the probable original saline contents are exhausted. The 

 most prolific " pans " in the mineral are those situated on 

 the Ballochmyle and Mona Vale estates, which in favour- 

 able dry seasons have been known to yield many tons of 

 salt. The surface of the '' pans " is during the dry season 

 coated with an efflorescence of the salt, by the 

 evaporation of the water, to a depth often as much as 

 2 inches in thickness. This has been scraped up for 

 domestic use, and the lower or contaminated portion used 

 for manure. The supply is apparently renewed without 

 any reported diminution in quantity year by year, as 

 evidenced by the fact that quite recently some at least 

 of the " pans " were observed to be coated with the white 

 incrustation of the salt. It has been stated that this salt 

 was formerly a source of wealth to the now extinct 

 aboriginals, who laid claim to the surrounding lands, and 

 the vicinity was often the scene of hotly contested battle 

 and bloodshed. (Pro. Eoy. Soc. Tas.,' 1889, pp. xxii.- 



XXIII.). 



146. Halloysite (Hydrated Silicate of Aluminium). 



This extremely unsatisfactory substance is presumed to 

 contain more silica than kaolin and more aluminium than 

 smectite, but there may be an indefinite variation from 

 one to the other. When it contains an admixture of iron 

 oxide it varies to a substance that is known as bole. It 

 occurs at numerous localities. 



147. Halotrichite (Hydrous Sulphate of Iron and 



Aluminium). 



This iron alum occurs at several localities as an efflor- 

 escence or as small stalactitic growths in old mine work- 

 ings. It also forms fibrous silky masses, which are com- 

 monly stained with iron oxide. It has been found at 

 Alberton, Mt. Heemskirk and other Dlaoes 



148. Hauynite (Ortliosilicate of Sodium, Calcium, and 



Aluminium, with some Sidphate of Sodium.) 



This is a rare alkaline accessory rock-forming mineral 

 which is usually associated with such minerals as nephelite 

 and leucite. In crystallisation it is cubical, and its habit 

 Affects the rhombic dodecahedron, but it is generally in 



