228 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY 



In many parts of the world wolfram and cassiterite are known 

 ltT „ to occur in pegmatite veins with quartz, felspar. 



Wolfram and cassi- . , f, ° . , rn , x . l 



torito in pegmatites. mica and other minerals. Ihere is some rea- 



son to believe that many of the true quartz 

 veins of Tavoy which contain wolfram and cassiterite, or both 

 minerals, with mica and no felspar, represent a specialised variety 

 of pegmatite formation. At Pagaye mine, at Osman Musti Khan's 

 Sinbo Sinma mine and at other places, pegmatites, using the term 

 in the ordinarily accepted sense, occur, in wliich wolfram exists 

 in comparatively large quantities and has been profitably extracted. 

 At the former mine the associated minerals are microcline felspar. 

 mica, green fluorite, scheelite and cassiterite together with pyrite, 

 ohalcopyrite and covcllite. A diagram showing the Structure of 

 the rock is given below. 



Both wolfram and cassiterite occur in greisens, narrow bands of 



, t7 „ , . quartz-mica rock formed by alteration of the 



i\ olfram and cassi- * ., ,. . . . , 



tei-ite in groisons. granite adjoining quartz veins, and are some- 



times present in sufficient quantities to make 

 the greisen bands a profitable source of ore. Bands of greisen are 

 sometimes observed traversing granite and containing little or no 

 signs of any vein quartz. In such cases the mineralizing gases 

 or solutions appear to have been injected through narrow films 

 or cracks in the original rock. These occurrences occasionally 

 contain wolfram and cassiterite and their destruction by atmospheric 

 agencies may give rise to valuable surface deposits of both minerals. 

 even in the absence of quartz veins of any noteworthy size. 



Pyrite- 



Pynte 

 i 



Wolfram- 



Felspa 



QJk* ihr gwrt*: if* I J 



Green Mica"~ 





spar L^- Vr-~-~-~- - 



Mica wall 



■Cassiterite 



* 3 inches. ■> 



Diagram of a stringer in the Pagaye pegmatites. 



