49 



contained in a cabinet on the left of the entrance. Case 



127, at the lower end oi the room, contains picked specimens. 



*This case is kept covered to protect the specimens from Case 59- 



the action of light. Visitors are requested to carefully 



replace the cover. The exhibit consists of a series of the 



characteristic ores, followed by definite silver minerals, classified 



according to composition. 



Ores. — These are under five headings, viz., gossan, massive 

 carbonate ore, kaolin ore, garnet sandstone, sulphides. 



The gossan is often rich in manganese, and frequently forms 

 stalactitic masses, as shown by 1333 and 2C95, and on a larger 

 scale in case 127. 1091 shows embolite. 



The kaolin ore contains garnets and quartz ; it is undoubtedly 

 the material resulting from the alteration of felspathic rocks such 

 as gneiss. Iodide and chloro-bromide of silver are frequently 

 found in this class of ore; as will be seen further on, some of 

 the best specimens of iodyrite occur in the kaolin. The so-called 

 garnet-sandstone, or garnet-quartzite ore is a granular rock 

 consisting of garnet, rhodonite, and quartz more or less impreg- 

 nated with metallic sulphides ; the prevailing red colour is due 

 to the garnet and rhodonite. The sulphide ore itself is essentially 

 an intimate mixture of galena and zinc-blende. The blende is a 

 troublesome mineral to deal with in dressing and smelting, and 

 the problem of separating it from the galena, and converting it 

 into a useful article of commerce, such as zinc-white, is a very 

 diflScult one.t 



SiLYER MrNEHALS.— 6986, Native Silver on copper ore. 



5537, a pretty little specimen of crystallised cerussite, with 

 native silver scattered over the crystals. ,. 



* The copper, zinc, lead, and other minerals associated with the silver ores will be found 

 each under their respective headings. 



t The remarkable saddle reefs, which constitute the ore-bodies at Broken Hill, with the 

 exception of the Consols Lode, are not referred to here, as they cannot be illustrated by 

 hand specimens. A large collection of the metamorphic rocks wi.l be foui^d ia case 73. 



