VEIN MINERALS. 221 



The cuprous sulphide, covellite, CuS, is formed by the decom- 

 position of chalcopyrite, and the dark indigo- 

 blue films which often coat specimens of chal- 

 copyrite from Pagaye are believed to consist of this mineral. 



The sulphide of lead, galena, PbS, is the commonest ore of lead 

 and one of the rarer sulphide minerals of the 

 wolfram veins. It has been noticed in small 

 quantities at Hermyingyi, Pagaye and Kanbauk. It occurs with 

 pyrite, chalcopyrite and fiuorite in thin stringers and films at the 

 Peneichaung granite quarries. The best specimens are from Sein- 

 pyon near Natkyizin, where fine granular forms exhibiting the 

 brilliant facets of its cubical cleavage are obtained. A quartz 

 vein carrying galena crops out in Mergui sediments on the road 

 between Uthayan and Wumpo. Galena is recognised by its lead- 

 grey colour, its perfect cubical cleavage and its weight. It is 

 easily reduced on charcoal to metallic lead. 



The sulphide of zinc, ZnS, sphalerite or " black jack," occurs 



sparingly as a vein mineral in Tavov district. 

 Zinc blonde. x , . n x i j " 1 1 



It is generally found as a very dark brown 



or black massive variety known as marmatite, which contains 10 



per cent, or more of iron, possessing a pale brownish streak and a 



specific gravity of about 3*9. The best specimens come from 



the Rubber Mile mine near Kyaukmedaung. Blende also occurs 



at Kanbauk in a narrow vein intergrown with cellular pyrite 



and a little chalcopyrite, edged with dense vitreous quartz. It is 



not easy to distinguish in the matrix from wolfram, especially as 



it possesses a perfect cleavage. When separated however, its 



lower specific gravity is at once appreciated. 



The sulphide of antimony, stibnite, Sb 2 S 3 , has been found in 

 Paungdaw and at Zinba in wolfram veins. The 

 form it assumes is that of curved bands and 

 fibres closely packed together. It has perfect cleavage and a brilliant 

 metallic lustre which tarnishes somewhat on exposure to the air. 

 It is quite soft and can be cut with a knife, and is distinguished 

 from other sulphides by its easy fusibility. Massive groups of 

 radiated and curved stibnite crystals have been found in the Mergui 

 and Amherst districts. The radial cleavage surfaces of these speci- 

 mens are furrowed with narrow cross lines and steps. 



