BY W. F. PETTERD, C.M.Z.S. 117 



207. MiLLERiTE (Sulphide of Nickel). 



Occurs in the form of delicate brass-like fibres, usually 

 in the fissures of serpentine and other rocks. It may have 

 been introduced into the rock as nickeliferous pyrites. 

 The pure mineral contains approximately 64 per cent, of 

 nickel. 



Occurs as capillary filaments near Leslie Junction, Dun- 

 das, with pentlandite ; in serpentine near the Colebrook. 

 It has been reported to occur with galena and other min- 

 erals at the old silver mine at the Penguin. At the Blue 

 Tier, near Beaconsfield, it has been noticed in small quan- 

 tity. 



208. MiMETiTE (Chloroarsenate of Lead). 



This and its congener pyromorphite are not by any means 

 rare species, since they are commonly found in more or 

 less quantity in the upper levels of many lead mines, where 

 they doubtless originate from the decomposition of galena, 

 the alteration of arsenopyrite affording, directly or 

 indirectly, the acid radical to the lead for the mimetite. 

 Isomorphous admixtures, with its ally pyromorphite, are 

 abundant ; in fact the one grades into the other imper- 

 ceptibly, and they have several characteristics in common. 

 They exhibit optical anomalies ; the chloro-arsenate is 

 always biaxial, and the chloro-phosphate is uniaxial ; in 

 proportion to the degree of admixture of the firstmentioned 

 it changes to the biaxial. Both crystallise in the hexagonal 

 system. At times there may be a pronounced curv^ature of 

 the prism faces to such a degree as to form almost spherical 

 masses. This variety is known as campylite. 



Occurs in minute bunches of crystals on the wall of the 

 lode at the Hampshire Silver Mine ; at the Magnet Mine 

 the mineral is often found in well-formed crystals, which 

 are from almost colourless to the normal brown. Occurs 

 at the Britannia and other Zeehan silver-lead mines ; at 

 the Hercules in white to dark-brown crystal groups : at 

 North-East Dundas it has been obtained in the usual small 

 crystals, at times fairly plentiful. 



Variety — Chromiferous Mimetite. 

 This variety never assumes the barrel-like shape so 

 common to the typical mineral. It is found in short 

 hexagonal prisms and plates, with basal terminations, 

 usually about 1 millimeter in breadth and length. The 

 colour varies from a decided brownish-green to deep 

 orange ; it is shining and opaque. The streak is orange 



