Quartz Veins and Mineralised Masses 



191 



secondary muscovite (sericite) in abundance in the forms of tufts and 

 rosettes, whilst in parts the original alkali feldspar of the rock is 

 replaced almost entirely by patches of sericite. Small granules of 

 epidote and of zoisite are present in parts of the aplite in some 

 abundance, but these minerals are, as a rule, only sparsely distributed 

 through the rock. Some parts of it contain only a few plates of 

 carbonates, in others, they are abundant, whilst in places they, in 

 company with quartz, form veins traversing it. Cupriferous iron- 

 pyrites in the form of small cubical crystals occurs all through the 

 aplite, in parts being only sparsely distributed, in others, especially in 

 and near the veins of carbonates and quartz, being present in relative 

 abundance. 



The jjatches of original quartz in the aplite generally show strain- 

 shadows, whilst the lamellae of the feldspars are usually bent and not 

 unfrequently broken. 



Some of the specimens from the deeper parts of the mass of the 

 aplite have more the characteristics of a granitite than of an aplite. 

 They contain a few plates of a pale-blue hornblende, a few laths of 

 muscovite, and many patches of biotite — much altered and largely 

 changed to aggregates of pale mica, chlorite and epidote, with, in 

 places, the extrusion of a good deal of magnetite. 



The portions of the mass richest in ferro-magnesian minerals, when 

 examined in thin slices under the microscope, supply evidence that 

 these minerals represent portions of the country rock through which 

 the aplite was intruded, and that they were taken up and absorbed by it. 



Two complete analyses of the aplite have been made in the 

 Government Laboratory with the following results : — 



