BY W. F. PETTERD, C.M.Z.S. 29 



mately associated with tetrahedrite and pyrit-e. The bis- 

 muth sulphide occurs as spiculated blades more or less 

 compact, which are very irregularly disseminated through- 

 out the minerals referred to. At the Mt. Black Mine, 

 situated near Rosebery, it has been detached in limited 

 quantity closely associated with chalcopyrite, pyrite, and 

 fiuorite, both purple and greenish, with a small but 

 appreciable amount of amorphous wolframite and intensely 

 black finely-radiating tourmaline. The most important 

 occurrence of bismuthinite known to exist in the island 

 is that of the Shepherd and Murphy Tin-Wolfram-Bismuth 

 Mine at Bell Mount, Middlesex. The mineral appears in 

 what seems to be a series of small lodes, which are 

 much faulted, but regular in the direction of throw, 

 and with a general strike east and west. They occur at or 

 near the contact of quartzite and a metamorphic yellow 

 garnet rock, the latter constantly without crystallisation, 

 and comparatively soft near its junction with the former, 

 but hardening gradually and imperceptibly at a distance 

 from the lodes, being finally in part capped with black 

 vesicular basalt of the Tertiary type. The harder garnet 

 rock contains much magnetite and a salmon-coloured min- 

 eral. The series of small lodes occurs in both the quartz- 

 ite and garnet rocks, and all have a general quartz gangue, 

 which is often crystallised in and about the numerous 

 small vughs which are commonly met with in practical 

 mining operations ; some topaz is always present in small 

 crystals, and a prosopite-like mineral is not uncommon, but 

 usually altered to achlusite. Fiuorite of various colours is 

 plentiful, but not in the crystallised form ; the m.ain 

 colours are purple and green, as is usually the case. The 

 bismuthinite is much altered to the carbonate of the metal 

 in the upper workings, and is accompanied by pyrite, 

 and the associates are wolframite, at times in small 

 crystals or crystalline masses, and intensely black cas- 

 siterite in small crystals and groups. Many of the latter 

 are geniculate, and, with the other metallic minerals, 

 are often imbedded in a white lithomargic substance. 

 Molybdenite in small but fairly well-developed crystals 

 is occasionally met with. The blades of bismuth- 

 inite are often attached to quartz crystals in the inter- 

 stices of the gangue, and they are not uncommonly, as fine 

 needles, found embedded in the white lithomargic material 

 and crevices of fiuorite. Terminated crystals of bismufh- 

 inite are unknown. The acicular crystals sometimes occur 

 grouped in the cavernous quartz gangue, or they may be 



