426 Transactions. — Geology. 



MnOa, wliicli occurs pure in Pyrolusite, is the most valuable, on account 

 of its parting readily with its oxygen to substances capable of combining 

 with it, and on this property depends the value of the ore in the generation 

 of chlorine for bleaching purposes, the decolourization of glass where sub- 

 oxides of this metal form the colouring matter, and also in its recent 

 application to the oxidation of phosphorus, etc., in the process of iron 

 manufacture. 



Manganese, however, also occurs in other forms, which require mention 

 as minerals. 



Diallogite, MnC. — The occurrence of this mineral is mentioned by Mr. 

 Skey (Geol. Eep. 1870-71, p. 85) associated with Calamine from a claim 

 high up the Tararu Creek, Thames, and presented by the manager of 

 Eussell's battery. 



He says : " The Diallogite of this specimen contains a portion of car- 

 bonate of lime, but the amount has not yet been ascertained. It is coloured 

 with oxide of iron, and crystallized in large rhombohedrons. The carbonate 

 of lime forms lustrous transparent crystals attached to the former, but 

 always external. These are always well shaped, but comparatively small. 

 They are interspersed somewhat rarely with small rock crystals." I regret 

 that I have been unable to find this specimen. 



A massive, flesh-coloured, specimen of this mineral was also collected 

 by Dr. Hector, November, 1881, in Makara Valley, where it occurs on 

 Mr. Thos. Eobmson's property. 



Ilhodonite or Manganese Spar, Mn Si. — The occurrence of this mineral at 

 Kawarau and Clutha is mentioned (Jurors' Kep. N.Z. Ex., 1865, p. 265), 

 and at the Pioneer claim, Dunstan (Jurors' Eep., p. 413), and it has also 

 been found in Canterbury and Waiheke. 



Hauerite, Mn". — In a paper read before this Society during the last 

 session, I mentioned the occurrence of this mineral, as determined by Mr. 

 Skey in rocks from the Wakatipu district, collected by Mr. McKay, and I 

 have now to mention its occurrence in certain specimens forwarded by Mr. 

 H. P. Washbourn fi"om Collingwood, where it occurs in crystals composed 

 of the cube and rhombic dodecahedron. 



Dana only mentions this mineral as occurring at Kalinka in Hungary, 

 in clay with gypsum and sulphur, in a region something like a solfatara, 

 but the Mangan-blende or Alabaudine which is a subsulphide of manganese, 

 he states, occurs in veins in the gold mines of Nagyag in Transylvania, 

 associated with Tellurium, carbonate of manganese and quartz. It is inter- 

 esting, therefore, to note the occurrence of Hauerite in crystalline schistose 

 rocks, and I was led by this to examine ores from other countries to see 

 whether it ever did occur under similar conditions. The result of this 



