428 ' Transactions. — Geology. 



One of these specimens shows the tufanite"(pyritous propylite) forming 

 one side of the vugh or cavity, on which a layer ahout f-inch thick of 

 fibrous crystalHne quartz has been formed. At the base of the specimen a 

 quartz leader about 3 inches wide and crystallized in small vughs near the 

 centre is inserted through the lining of the cavity, which is formed by the 

 junction of two small veins. This leader is traversed by small strings of 

 crystals of Mispickel or Leucopyrite, and on the internal quartz coating of 

 the cavity Calcite has crystallized at places in large rhombohedral forms, 

 and at others the arsenic has been deposited in reniform masses. 



On the faces of the Calcite crystals small globular patches of arsenic 

 have formed, and stalagmitic incrustations of Calcite, with alternate layers 

 of arsenic, have been built up on these, forming fine reniform masses. 

 At one point, near the top of the specimen, minute quartz crystals can be 

 seen, also Calcite forming hollow pseudomorphs of quartz, all the cavities 

 of which are filled with the most beautiful filaments of gold ; a few crystals 

 of Mispickel are here visible. 



The other specimen is of a massive reniform character, and is deposited 

 on the quartz lining of the vugh without the interposition of Calcite as in 

 the first specimen. 



Mispickel, Fe"+FeAs, or arsenical iron pyrites, is by no means un- 

 common in New Zealand. It is mentioned by Dr. Hector, (Jurors' Rep. 

 N.Z, Ex., pp. 265, 486), as occurring in magnesian felstone and diorite 

 in Milford Sound, and also in alluvial drifts at Waipori and elsewhere, 

 and is again referred to by Professor Liversidge, in his description of 

 the minerals of the Otago Museum (Trans. N.Z. Inst. vol. x., p. 502). At 

 page 257 of the Jurors' Reports, above cited, this mineral is mentioned in 

 Dr. Haast's collection as occurring in diorite at the Malvern Hills. 



Specimens have been collected by Mr. McKay from the Buckleburn, 

 on Wakatipu Lake, as fine crystals imbedded in chlorite schists, and, as 

 previously mentioned, it occurs in the auriferous leaders of the Kapanga 

 mine, and is found in most other auriferous reefs. Specimens brought by 

 Dr. Hector from Langdon's lower reef, near Greymouth, proved to be highly 

 auriferous, the assay of the sample showing 69 ozs. 3 dwts. 12 grs. of gold, 

 and 2 ozs. 9 dwts. 19 grs. silver, to the ton, a considerable proportion of 

 it, however, being in a free state. 



I collected specimens of the same mineral from the Perseverance mine, 

 Collingwood, where it occurs in very characteristic rhombic crystals, in a 

 white granular quartz, but contains very little gold. 



As a rule this class of pyrites is the most highly auriferous, although 

 at times gold also occurs largely in the more common form of iron 

 pyrites. 



