222 BROWN & HERON. GEOLOGY AND ORE DEPOSITS OF TA\0\ 



The sulphide of bismuth, bismuthinite, Bi 2 S 3 , was first recognised in 



„. t .. u fine hairlike crystals. According to Dr. Morrow 



Bismuthinite. ~ , „ ,, m / . , . . , , . , . 



Campbell, J he sulphide of bismuth is some- 

 what more widely distributed [than the native metalj, though not by 

 any means common. It occurs in the same veins with wolfram, cassi- 

 terite and molybdenite, often in contact with the two former, also 

 associated with them as a primary mineral in granite. It is 

 always fibrous in structure, steel-grey in colour with high metallic 

 lustre. Sometimes it is hair-like in separate fibres. It is often 

 found in microscopic crystals throughout quartz to which it gives 

 a smoky-black to black appearance. When exposed to the air it loses 

 its lustre turning black then grey to green and finally pale yellow. 

 The simplest test for bismuth is to place a fragment in a little cold 

 hydrochloric acid not sufficient to dissolve it completely, wait 

 a few minutes till action has ceased, pour the acid into a glass of 

 water, it will turn milky and a heavy white precipitate will fall " 

 [if bismuth is present]. 1 



Bismuthinite has been found at Kalonta, Zinba, Paungdaw and 

 Pagaye. 



Pyrrhotite is a sulphide of iron of doubtful composition though 

 the best authorities agree that it conforms to the 



neSf^St^ " ""*" 8 eneral formula »«A+* It is a rare mineral 



in Tavoy except in the Kadando vein where it 

 occurs abundantly with pyrite, chalcopyrite and wolfram. It has a 

 peculiar bronze colour when fresh but in the Tavoy climate it tarnishes 

 in a few days to a dark metallic grey. In this condition it can 

 easily be mistaken for other tarnished sulphides but its magnetic pro- 

 perties and the colour of a fresh fracture furnish discriminating tests. 

 The sulpharsenide of iron, FeAsS, arsenical pyrites or mis- 



pickel, is a rare mineral in Tavoy. It is 

 Arsenopyrite. , . ,. m . . J . 



common at the lagu mines in Mergui where 



it is found in compact massive forms with irregular surfaces of a 



light steel grey colour. It has a hardness of 5£ and a specific gravity 



of 6. It is an important ore of arsenic in some parts of the world. 



Carbonates. 

 The carbonate of iron, siderite, Fe 2 C0 3 , which is also known as 



„., t. chalybite, has been observed as a vein mineral 



Siderite. J ' 



only at Kanbauk, where it occurs as pale brown 

 1 J. Morrow Campbell (9), p. 24. 



