Pond. — On Manganese Deposits in AucJcland. 357 



for a given quantity of chlorine ; and, as it is purchased on the 

 assay- value of peroxide present, the freight and shipping 

 charges are proportionately less to its value. In this case, 

 however, we are viewing the percentage of peroxide, and this 

 alone is of value for bleaching purposes ; but during the last 

 few years an extensive demand has sprung up for manganese 

 for the purposes of producing an alloy with iron to form 

 Spiegel, manganese bronze, &c., and in this demand the form 

 of oxide in which the manganese is present is not of so much 

 moment as the extent to which the metallic element itself is 

 present is concerned. Hence the lower oxides of manganese 

 are available for this purpose ; but in this case it is required to 

 be as free as possible from phosphorus, sulphur and earthy 

 matter, silica, &c. Both of these elements — phosphorus and 

 sulphur — are pernicious in the manufactured Spiegel, and every 

 effort is made to procure samples as free as possible from these 

 objectionable materials ; the objection to the silica being 

 chiefly on account of the loss of iron in the process of fusion, 

 by the combination of silicate of iron in the slag. Frequent in- 

 quiries reach me from England as to the presence or otherwise 

 of cobalt in our manganese ores, while sometimes I am asked 

 as to the presence of a payable percentage of copper. Hitherto 

 I have not found cobalt in these ores beyond traces, though 

 I have found it in combination w^ith the manganese wads, a 

 matter which I have already brought before the Institute. 

 With regard to copper, I have not found it in combination with 

 any of the ores examined by me, though I have made analyses 

 of several samples brought to me and purporting to be copper- 

 bearing. 



The effort to ship only high-class ores has resulted in such 

 samples being fahly free from gangue in some instances, 

 though in others they reach 20 per cent., the iron- oxides 

 present varying from 4 to 10 per cent. In a few instances I 

 have examined these ores for phosphorus, and find it present 

 to the extent of from 0-188 to 0-3 per cent., though it may 

 very probably run higher in some samples. 



By the advance of scientific research, and adaptation of 

 knowledge so gained, means have been found in the manu- 

 facture of bleaching-powder, in which the great bulk of the 

 manganese is used, to recover the spent ore, and re-utilise 

 the material an unlimited number of times. The cost of 

 this recovery, however, is at present a known quantity, and 

 this cost largely governs the market-value of the ore. In 

 consequence of this the price of manganese has greatly re- 

 ceded during the last few years, and it is now not much more 

 than one-half the value of its selling-price in the London 

 market during 1880-82. This has naturally largely governed 

 the output of our district, which at one time promised to 



