BY W. F. PETTERD, C.M.Z.S. 147 



schistose rocks which are characteristic of the localities 

 indicated. 



" At the North Lyell Mine a compact massive form of 

 this substance occurs. It is of a pale-green colour, has 

 a smooth and unctuous feel, and exhibits distinct trans- 

 lucency at the margin of thin flakes. 



''Upon analysis it gives the following result: — 



Per cent. 

 Si O2 = 59-0 



AI2 O3 = 32 -05 



Combined H2 = 7-2 



98-25 



The oxygen ratio is 31 '5 : 15' 1, practically resembling 

 the mineral from the Chester Mine, North Pieman." (R. 

 Sticht.) 



269. Pyrostilpnite (Silver Sulphantimonite ). 



A rare ore of silver (containing 59*44 per cent, of Ag) 

 known as " fire-blende." It crystallises in the monoclinic 

 system, and is sometimes tabular, but its common habit is 

 in imperfectly terminated sheaves or irregular bunches — 

 like stilbite — but of almost microscopic dimensions. It is 

 of a hyacinth-red colour, but is generally tarnished to 

 an almost black discolouration. When free from dis- 

 colouration it has an adamantine lustre and decided red 

 streak. In minute vughs it may be detected in associa- 

 tion with nests of small quartz crystals. When coating 

 cleavages in its extremiely silicious gangue it soon arrests 

 attention from its peculiar habit of occurrence in radiating 

 and irregular bunches, by which feature it may be known 

 from proustite, although both have the same bright colour. 

 Before the blow-pipe it fuses easily, giving off white anti- 

 monial fumes, and with soda affords a bead of silver. It 

 occurs in limited quantity, but quite enough to make an 

 appreciable difference in the bulk silver assays. Locality : 

 The Long Tunnel Mine, Heazlewood. Associated with this 

 is another silver mineral of an orange-yellow colour with 

 yellow streak. It affects a frondose habit, and is found 

 in exceedingly limited quantity as aggregates in the cleav- 

 ages of the gangue. It may be xanthoconite (a silver 

 sulpharsenate, crystallising in the rhombohedral system), 

 but the quantity is too small to make reasonably certain 

 of its exact identification. Pyrostilpnite occurs at the 

 Oonah Mine, Zeehan, closely associated with pyrite in cellu- 

 lar quartz. 



