204 THE MINERALS OF TASMANIA. 



Part 2, 1905): — "Mr. Petterd is of opinion that the 

 mineral is a product of contact metamorphism in granite 

 country. The zircon is accompanied by blue sapphires, 

 menaccanite, and other detrital minerals. One fairly well- 

 developed, doubly-terminated crystal was determined. 

 The forms present are a (100), m (110), p (111), v (221), 

 u (331), and x (131), of which a and jj predominate. The 

 crystal is dark-red in colour, and shows a striated area in 

 one part. All the forms are present with the full com- 

 plement of faces, except u. which has but two. The crystal 

 measures approximately 10 mm. in diameter. Sp. g., 

 4-57." 



354. ZiNKENiTE ( Sulpha jitimoniate of Lead). 

 Although this mineral is known to crystallise in the 



orthorhombic system the crystals are rarely distinct, and 

 are extremely rare. It occurs plentifully in the massive 

 form at the south workings No. 1 level. Magnet Mine. 

 It is constantly semi-fibrous, with an uneven fracture, 

 metallic lustre, and steel-grey colour. As occurring at the 

 locality mentioned it is highly argentiferous, often con- 

 taining hundreds of ounces of silver to the ton. It is 

 associated with galena, pyrites, and dolomite. In its 

 fractures and joints there occurs a peculiar secondary 

 mineral, which is exclusively derived from its decomposi- 

 tion. This secondary mineral assumes the form of very 

 small discs composed of divergent milk-white spicules, 

 which are commonly clustered together in radial form. 

 They have a bright shining lustre, and hardness of about 

 1*5. They are closely attached to their base, and of such 

 extreme tenuity that it is practically impossible to secure 

 enough material for a satisfactory analysis. A minute 

 quantity before the blowpipe gave the qualitative reactions 

 for sulphur, antimony, and lead, with H2 O. It appears to 

 be a basic sulphate of the metals mentioned, and is in all 

 probability a new compound closely allied to lamproph- 

 anite. 



355. ZiNNWALDiTE (Lithia MuscovifeJ. 



This is the characteristic white mica of the stanniferous 

 granites, and as such it occurs in the old tin-mining local- 

 ities, such as Zinnwald, Altenberg, and similarly in Corn- 

 wall. It is consequently abundant throughout the tin- 

 bearing granites of the east coast mining district, and the 

 same applies to the Ben Lomond, Heemskirk, and other 



