ON THE BARRIER RANGES SILVER FIELD. 193 



Along an approximate extension of this same horizon, both 

 north-east and south-west, though not proved to be continuous, 

 are found similar zones of carbonaceous-metalliferous rocks, par- 

 ticularly rich in silver. As some of the better developed mining 

 properties occurring in such zones the following may be mentioned, 

 around which, however, are grouped many others not so ex- 

 tensively prospected : Thackeringa, Umberumberka, Day Dream, 

 Apollyon, Terrible Dick, New Year, War Dance, &c, many of 

 these in some parts of their course appearing as contact vein 

 deposits between crystalline schists, generally graphitic, and 

 granitic or dioritic rocks ; a characteristic feature of the veins 

 occurring in these graphite bearing rocks being that their 

 enclosed iron ores are invariably in the form of carbonates, in 

 most cases superficially changed to limonite, or more rarely to 

 haematite. This change of siderite into limonite of similar density 

 has been accompanied by a decrease in volume, which should be 

 equal to nearly one-fifth. These changes, having taken place 

 from joints and crevices and proceeding from the outer side 

 inwards, have resulted either in spongy masses or compact crusts, 

 enclosing cavities of various dimensions, in which are often found 

 accumulated the ores of lead, zinc, silver, copper, &c, which 

 appear to have been originally disseminated through the siderite. 

 Silver chloride is frequently found in these cavities, sometimes in 

 large masses, generally associated with lead, antimony, copper, 

 and sometimes zinc. These deposits, while buried in the rocks, 

 have been largely protected from the actions of alkaline and 

 earthy sulphated waters, but where ' by disintegration of the 

 surface they have been brought to or above the present horizon, 

 and their enclosing iron removed by deoxidation, they have been 

 set free as surface slugs, where by further concentration, due to 

 their associating metals being less stable in the presence of pre- 

 vailing atmospheric agencies, they are found in a comparatively 

 pure state, oftentimes having only an incrustation of carbonate 

 of lime or oxide of iron. Native silver is also found in many of 

 these veins, sometimes in the form of wire in cavities in the lead 

 or iron, but frequently lining crevices or disseminated through 

 the lead ores. Some of these veins are extremely rich, yielding 

 large returns for small out-puts, a vein one or two inches wide 

 often containing sufficient silver to cover all working expenses. 



There is another class of ore deposits apparently due either to 

 the imperfect filling of veins, generally of the first class, or to 

 fractures arising from local contractions, rather than to extensive 

 earth movements. Solutions circulating through these have de- 

 posited their metallic and other salts as chemical affinities directed, 

 one or other of the metallic ores being often concentrated round 

 certain points, forming bunches or banded deposits, or otherwise 



M— Noyember 5, 1896. 



