BY AV. F. PETTERD, C.M.Z.S. 45 



nodules of the black basalt, which clearly show the 

 implanted crystal groups, are often met with in the 

 streams, and are sometimes mixed with other species of 

 zeolitic minerals and ferro-calcite. 



The crystals from Bell Mount, Middlesex, have been 

 examined by Dr. C. Anderson, who states (" Records of 

 the Australian Museum," Vol. VI., Part 5, 1907) :— '• Some 

 fine crystals, '75 to I'd cm. in diameter, have been found 

 loose and coating a vugh in Tertiary basalt at this locality. 

 Like the Ben Lomond and Inverell minerals, these are 

 penetration twins on the vertical axis, but they differ 

 from the former in the presence of a (1120) and t (1123)." 



70. Chalcocite (Sulphide of CopperJ. 



This, notwithstanding the large quantity of copper pro- 

 duced by the State, is an extremely rare mineral, and 

 has only occurred at two or three localities. It crystallises 

 m the orthorhombic system with an empirical composition 

 of sulphur 20 per cent., and copper 80 per cent. = 100. 

 It is the native cupreous sulphide, and is also known as 

 copper glance, redruthite, and vitreous copper ore. It 

 usually occurs in the upper workings of the mines, and is 

 regarded as of secondary origin, produced by the altera- 

 tion of chalcopyrite or yellow ore. It is commonly of a 

 dark lead-gray colour, and is quite sectile and fusible — so 

 soft as to be easily cut with a knife, and so fusible as to 

 melt at a low heat. It is often reported to occur, but the 

 genuine native cupreous sulphide is, as a matter of fact, 

 but rarely obtained. In all probability the only true 

 occurrences were in the Mt. Lyell district, and then but 

 in extremely limited quantity. Crystalline masses of small 

 size have been obtained at the Lyell Blocks, among other 

 mines of the locality. Occurred at the King Jukes Mine, 

 Mt. Jukes. Small crystals have been found disseminated 

 on schist wdth bornite at the North Lyell Mine. It has 

 been obtained in blocks of many pounds weight with 

 native copper at the King Lyell Mine. Reported to occur 

 with quartz at Mt. Balfour. 



71. Chalcopyrite fSulpJude of Copper and Iron). 



This mineral crystallises in the tetragonal system. The 

 crystals are not by any means abundant ; they affect a 

 spheroidal habit and are very often distorted, with the 

 faces curved and striated. It is the common ore of cop- 

 per in almost all copper-producing countries. It is an 

 almost constant companion of cassiterite, although the 

 bane of the tin-miner. The mineral is of a rich golden 



