BY LEO A. COTTON. 76^5 



crystals frequently show a well marked series of layers parallel 

 to the crystal-faces. 



The minerals occurring in this type of vein are quartz, mica, 

 wolfram, bismuth, molybdenite, and fluorite. 



Tlie quartz occurs both massive and crystallised, and in the 

 centre of the reef. The crystallised quartz occurs most frequently 

 lining the vughs, and projecting inwards. The individual 

 crystals may be as much as 2 inches in diameter, and several inches 

 long. Occasionally there is a peculiar development of very flat 

 crystals, the distance between one pair of prism-faces being less 

 than \ of the width of the crystal. Double-ended quartz-crystals 

 are also very common. The crystallised quartz may be clear and 

 colourless, translucent or smoky. Some of the smoky quartz- 

 crystals contain so much impurity that they are quite opaque 

 when only about \ of an inch in thickness. Occasionally both 

 clear and smoky quartz-crystals are to be found invested in a 

 sheath of milk-white, opaque quartz, the thickness of which \^ 

 about ~^y the width of the crystal. 



The iniccL occurring in these veins has already been remarked 

 on. It cannot be certainly named until an analysis has been 

 made. As, however, the type of vein is similar to that previously 

 described* from near the Leviathan Mine, it is probable that the 

 mica is allied to the paragonite group. 



Wolframite is found both crystallised and massive. Its distri- 

 bution in the veins is similar to that of the cassiterite, and both 

 minerals may be obtained in the same hand-specimen. Platy 

 crystals are common, and a yellow ochreous mineral has been 

 observed between two diverging plates. The wolframite is 

 not abundant, for very little is obtained when cleaning the tin 

 for market. Its total weight is probably less than one per cent, 

 of the tin present at Elsmore. 



Topaz and tourmaline have not been observed, and cannot be 

 present in any quantit}^ 



* Cotton, Leo A., " Metasomatic Processes in a Cassiterite Vein from 

 New England." These Proceedings, 190^, p.2'20. 



