ON THE BARRIER RANGES SILVER FIELD. 187 



description of the various associations of these earthy and metallic 

 minerals, even were I prepared to do so, since they are not only 

 constantly changing at different horizons, but in different parts of 

 the lode at the same horizon. I shall therefore only notice a few 

 of their characteristic or prominent features. 



The following minerals are those most easily recognisable, as 

 making up the main portion of the lode : — Earthy minerals — 

 quartz, kaolin, garnet, gypsum, glauberite, apatite, and opal ; 

 Ferruginous — limonite, chromite, magnetite, franklinite, cacox- 

 enite and mispickel ; Manganese — pyrolusite, psilomelane, and 

 their various admixtures with iron ; Lead — cerussite, anglesite, 

 galena, pyromorphite, mimetesite, maldonite, wulfenite, percylite, 

 cotunnite and matlockite ; Copper — native-copper, cuprite, mala- 

 chite, azurite, olivenite, bournonite, chalcocite, melachonite, 

 atacamite, and chrysocolla ; Zinc — calamine, smithsonite and 

 zinc-blende ; Silver — -cerargyrite, embolite, iodargyrite, bromar- 

 gyrite, argentite and native silver. Of these the various ores of 

 iron and manganese, together with kaolin and quartz make up the 

 principal matrix of the lode in which occur irregularly distributed 

 the ore of lead, zinc, and silver, copper appearing to be more con- 

 fined to favourable positions, while the other minerals are found 

 in geodes, bunches, or sparingly disseminated through the gangue. 

 There appears to be no fixed laws of association (or paragenesis) 

 between these various minerals so far as observed. The different 

 combinations of silver with chlorine, bromine, and iodine are found 

 alike impregnating kaolin, porous iron-stone, and granular cerussite,. 

 anglesite, and quartz, often beauti fully crystallized in geodes, and 

 implanted in various shapes on stalactites of manganic iron. 

 Silicates and carbonates of zinc associate chiefly with the iron of 

 latest formation, such as the beautiful stalactitic formations of 

 interlaced rods and columns, sometimes resembling miniature 

 temples ; they are also found in granular cerussite, especially in the 

 vugs, while zinc blende, together with iron and copper sulphurets, 

 are generally found intercrystallized with galena. 



The sources of the various minerals and metallic ores here found 

 accumulated together, may reasonably be supposed to have been 

 threefold. First the feldspathic minerals, from which the kaolin 

 has been derived, together with a large portion of the quartz and 

 possibly metallic sulphurets and manganese, evidently belong to a 

 period of vein-filling by the upward circulation of heated alkaline 

 solutions, while such actions have been partly protected from the 

 disturbing influence of descending earthy and organic waters, 

 consequent on the present horizon being deeply overlaid by super- 

 incumbent rocks. Secondly during the removal of these upper 

 rocks, owing to their previous elevation and subaerial decompo- 

 sition by the agencies of earthy and organic solutions operating 



