8 THE MINERALS OF TASMANIA. 



anorthite. It is also termed andesine. As is usually the 

 case with the felspar group, it is always of a pale shade 

 of colour. It occurs as a constituent of the essexite of the 

 alkaline plexus of Port Cygnet, and has been recorded 

 from the Mt. Lyell district. 



14. Anglesite fSulfhate of Lead). 



Native sulphate of lead was named from its occurrence 

 in the island of Anglesea. With other sulphates, it is 

 formed by the oxidation of sulphides above water-level ; 

 that of lead being less soluble, it is often retained, while 

 the sulphates of zinc, copper, and iron are dissolved and 

 thus carried away in solution. Galenite is the natural 

 parent of anglesite, and wherever that mineral has been 

 shielded from the attack of carbonates, such as calcite, its 

 oxidation results in the formation of this secondary 

 mineral. It forms transparent to translucent crystals often 

 beautifully formed, belonging to the orthorhombic system ; 

 the lustre is adamantine, and they are readily scratched 

 by a knife. The mineral is often attached to decomposing 

 galena or implanted on gossany limonite. Numerous speci- 

 mens of exceptional size and perfection occurred at the 

 Comet Mine, Dundas. The characteristic dagger-shaped 

 crystals were of remarkable perfection, perhaps the finest 

 ever discovered in the Commonwealth. They often had 

 massicot implanted in the interstices, thus forming beauti- 

 ful specimens for the cabinet. It occurs sparingly at the 

 Zeehan and Whyte River silver-lead fields. At the latter 

 some pretty rhombic prisms with sharp pyramidal termina- 

 tions have been obtained, attached to the partially altered 

 galena, and again on ferruginous gossan. At the Magnet 

 Mine it has occurred of exceptional beauty, associated 

 with crocoisite and pyromorphite, usually in the capping 

 of the lode, well advanced in decomposition. It is often 

 reported to assay somewhat high in silver, in which case 

 that metal is practically intermixed in the form of a 

 haloid. 



Referring to the crystals of anglesite. Dr. Anderson 

 writes (" Records of the Australian Museum," Vol. VI., 

 Part 2, 1095): — ''In the museum collection there is one 

 specimen from this locality (Comet Mine, Dundas) con- 

 sisting of a group of well-developed lustrous crystals in 

 a vugh of galena, with powdery limonite. The crystals are 

 of a general habit. . . . The crystal there represented 

 measures \'2 cm. x 1*9 cm. ; it is slightly broken at the 

 end of the macro-axis, and the a (100) faces are strongly 



