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genetically related to the granite. The series comprises 

 microcline aplites and a number of albite pegmatites 

 (albitites), viz., quartz and muscovite albitites. These rocks 

 traverse the granite in the form of dykes, and also as irregular 

 masses, and represent the later stages of the crystallization 

 of the granitic magma. 



The microcline aplite intrusive mass is the home of the 

 quartz-tourmaline nodules now under discussion. This aplite, 

 known as the "Pink Aplite," occurs as a large intrusive 

 mass along the coast adjacent to the Cape Willoughby Light- 

 house. Its intrusive nature is well marked, the junction with 

 the granite being well defined. The mass shows a rather 

 variable texture throughout its extent. The greater part is 

 of very fine grain, but in part this grades into a coarser 

 variety, in which are developed phenocrysts of blue quartz, 

 and the ferromagnesian mineral biotite also makes its 

 appearance. 



The aplite has been fissured, and along these fissures 

 quartz veins have been intruded. Associated with these 

 veins occurs a zone of altered aplite consisting essentially of 

 quartz and a light-greenish mica. This is a greisen. A 

 further pneumatolytic change is the production along fissures 

 of white kaolin. 



At the south end of the mass there are developed, in the 

 very fine-grained variety, numerous patches, in cross section 

 roughly hexagonal to elliptical. On examination these 

 patches, or nodules, are seen to consist mainly of quartz and 

 tourmaline. 



The minerals recognized in the aplite are quartz and 

 felspar. Microscopically the minerals present are quartz, 

 microcline, plagioclase (albite), and, as accessories, biotite, 

 much chloritized, and muscovite. Kaolin and secondary 

 mica accompany the felspars as alteration products. In the 

 fine-grained varieties of aplite, biotite and muscovite are 

 usually absent, the development of these minerals being 

 relegated to the coarser varieties. 



The aplite is remarkable for the presence of occasional 

 granophyric phenocrysts of quartz and microcline, and micro- 

 graphic intergrowth of these two minerals is displayed, more 

 especially in the coarser varieties. In parts of the finer- 

 grained types the fabric approaches the type "granulitic," 

 characteristic of some aplites. 



III. The Quartz-tourmaline Nodules. 



These nodules, "on account of their mineralogical com- 

 position, resist the attack of the normal agents of weathering 



