Cox. — On the Mineralogy of New Zealand. 425 



Psilomelane, E Mn^+H. — H. 5-6, massive and botryoidal; colour, iron- 

 black passing to dark steel grey ; streak brownish-black ; shining, opaque. 



This mineral is mentioned in the Jurors' Eep. N.Z. Ex., 1865, p. 258, 

 as amongst Dr. Haast's collections. It was found in veins in the Upper 

 Waimakariri. 



It is also found at the Bay of Islands, where it occurs massive and forms 

 the most valuable ore ; at Kawau it is found both as a massive ore and 

 also as botryoidal incrustations ; and at Waiheke, Waipu, and Whan- 

 garei it also occurs, as well as at Ohariu, Wellington, associated with 

 Manganite. It also occurs in large quantities in the island of Pakihi, 

 Auckland, where it is found in numerous small veins, about 1 inch thick, 

 running generally parallel to the cleavage of the slates, but sometimes at 

 right-angles to it (Hutton, Trans. N.Z. Inst., vol. i., p. 168). 



It is a valuable ore of manganese, consisting, as it does, of a mixture of 

 MnO and MuOa, but varies greatly in its composition, containing many 

 impurities. 



Analysis op Psilomelane feom Bay of Islands. 

 Manganese oxides . . . . 75'46 



Ferric oxide . . . . . . 11'76 



Siliceous matter . . . . 2-74 



Water .. .. .. 10-04 



100-00 



Wad. — Composition various. Mn. (Ca. Ba. K.) Mn.^ + 3H. 



This is a soft, earthy form of manganese, which varies greatly in its 

 composition and general character, but includes all the softer hydrated 

 manganese ores. It was first mentioned, in 1870, by Captain Hutton, as 

 occurring in considerable quantities, associated with Calcite, in the Black 

 Eeef, at Tararu Creek, Thames (Gleol. Eep. 1870-71, p. 5), and has also 

 been found at Waiheke, Bay of Islands, Auckland, Napier, Whangarei, and 

 Flaxbourne, and indeed occurs generally wherever other ores of manganese 

 are found. It frequently forms an important ore of that metal, having a 

 similar composition to Psilomelane, but containing a greater quantity of 

 water, and varying more than that ore in the quantity of manganese which 

 it contains. 



Analyses of these ores show that they contain from 27*14 to 87*47 per 

 cent, of oxide of manganese ; from 12-05 to 28' 1 per cent, of water, and 

 from "42 to 42*83 per cent, of silica. 



The foregoing are the only ores of manganese which can be looked upon 

 as of economic value, since their usefulness depends upon the amount of 

 oxygen which they contain combined with the metal ; and the black oxide, 



46 



