BY W. F. PETTERD, C.M.Z.S. 107 



yellow, by which it may be known from hematite and mag- 

 netite. It often forms a cementing medium of breccias 

 and conglomerates. At Dundas is occurs pseudomorphous 

 after siderite, and is then known locally as '" tomahawk 

 iron." On the banks of the River Tamar extinct Tertiary 

 species of fresh-water bivalves belonging to the genus Unio 

 are occasionally obtained, similarly changed to limonite. 

 At Beaconsfield, at the eastern tinfields, and at the Savage 

 River crystals of pyrites have been found altered in the 

 same manner. It is abundant at the Heazlewood, Mere- 

 dith Range, Savage River, Ilfracombe, Beaconsfield, 

 Blythe, Dial Range^ Mt. Claude, Middlesex, Housetop, 

 Mt. Lyell, King River, Mt. Ramsay, Mt. Read, Magnet, 

 Bischoff, Dundas, Zeehan, and many other localities. 

 Much of the material usually termed gossan on all the 

 mining fields in this State, in common with what prevails 

 in most mineral-producing centres, is limonite. In mineral 

 veins carrying the unstable pyrites, chalybite, or other 

 iron-bearing minerals, it is usual to find the capping or 

 Tipper portion of the mass consisting of much brown oxide 

 of iron, more or less contaminated, or otherwise gossan. 

 This alteration is created by oxidising agencies. This 

 characteristic is almost invariable in regard to copper- 

 bearing ore-bodies, or any lode containing pyrites in any 

 form, and in this State is a prevailing feature of our 

 larger metallic veins. Sometimes the rusty material is 

 in connection with quartz as gangue, and then the latter 

 is generally honeycombed, due to the loss of the original 

 pyrite. The presumed connection between the outcrop and 

 the ore which may exist below is expressed by the old 

 adage — 



" A lode that wears no iron hat 

 Is never likely to be fat." 

 The ferric hydrate or limonite occupies naturally only the 

 superficial portion of the lode or vein, or above the water- 

 level of the country below which the primary sulphide of 

 the metals may be expected to occur with little alteration. 

 Enormous masses of this substance have been worked at 

 many of the mines occurring in this State, notably at the 

 West Comet, Hercules, and Magnet. At the Hercules 

 much of the gossan contained payable quantities of both 

 gold and silver. A limited quantity was exceedingly rich — 

 up to as high as 20 oz. of Au with 3 to 400 oz. of Ag. 

 At the lastmentioned mine many thousands of tons have 

 iDeen mined, containing high values in both lead and silver, 

 the former in the form of disseminated oxide and car- 



