76 THE MINERALS OF TASMANIA. 



of the secondary derivatives. Galena easily tarnishes, in 

 which case it sometimes shows a brilliantly iridescent sur- 

 face, exhibiting beautifully striking shades of blue-green 

 and red. This phenomenon is specially noticeable in much 

 of the ore obtained at the Junction and Queen Mines at 

 Zeehan. Cavities occurring within the zone of oxidation 

 often exhibit a marginal coating of unaltered galena, with 

 beautifully developed complex crystals of cerussite in the 

 interior. 



The coarsely crystalline ore is generally considered to be 

 poor in silver contents, but this is not always the case, as 

 such an ore may at times contain higher values in silver 

 than the steel-grained material which, among miners, is so 

 universally considered such an acquisition. As a rule lead 

 sulphide is richer in silver from lodes occurring in slate, 

 less so when from granite, and is commonly poor in the 

 desired companion when from limestone. 



Many of the silver-lead lodes occurring in the Zeehan 

 'mining district exhibit, especially near the walls, an 

 unmistakable graphitic substance, which appears not to 

 have originated from altered organic matter, but rather 

 perhaps from the decomposition of metallic carbides of 

 deep-seated origin under favourable conditions. At the 

 Sylvester Mine, Zeehan, a large quantity of beautiful 

 dark-green pyromorphite, with lesser quantity of cerussite, 

 overcapped the lead ore. Native silver, often in arbores- 

 cent patches, has been frequently obtained attached to the 

 galena, notably at several of the Zeehan mines; and at 

 the Murchison, at Farrell, and at the Godkin Mine, Whyte 

 River. At the Comet Mine, Dundas, an extensive body of 

 argentiferous carbonate lead-ore has been worked ; it 

 formed a capping to the primary lead ore. The ferro- 

 mangansse lode-capping, or gossan, of the Adelaide and the 

 West Comet Mines in t'he same locality have br^come some- 

 what celebrated for the wonderfully fine masses of cro- 

 coisite which they have afforded. Tlie unusual association 

 of magnetite with galena occurs at the Kynance Mine at 

 Zeehan. At the Farrell Mine, at Tullah, a remarkable 

 pipe of galena has been worked, which in portion showed a 

 quantity of greenish lithomarge surrounding and 

 throughout which occurred a ronsiderable number of 

 finely-developed galena crystals, varying in size from 

 very diminutive to about 1 inch in length. (.'hey 

 represent mainly cubo-octahedra and perfect octa- 

 hedra ; many single with excellent terminations, while 

 others are irregularly bunched together. They may be said 



