58 SUPPLEMENTARY NOTE ON LTMURITE. 



axinite quartz veins, on the West Coast P.A. sections,. 

 cl(>sf ro tlie li'i'anite. A slide })repare(l from this vein rock 

 shows axinite, quartz, and an al)undance of leucoxene. It 

 is notewortliy that the axinite is confined to the vein stuff, 

 as in Oornwall, hut there is no occurrence of liniurite. 



Boron vai)ours, existing in the magma, and evolved 

 during crystallisation, undoubtedly play a part in produc- 

 ing both tourmaline and axinite. In Cornwall both tour- 

 maline and axinite are found in the granite contact zone, 

 while other rocks, sometimes basic igneous ones, have been 

 acted upon by granite with the same results. In the 

 Hartz axinite and tourmaline occur at the contact of 

 granite and diabase, and this led Lossen to correlate these 

 two minerals. " In view of these facts, it seems to us very 

 likely that the Western granite or its elvans and the 

 Coiebrook pyroxinite consolidated contemporaneously. 

 Plutonic solfata)'ic i)rocesses, which were plainly in opera- 

 tion in the granite area, as shown by the tourmaline and 

 axinite just referred to, may very well have liberated the 

 boron vapotirs, which, travelling eastwards by easily 

 imaginable channels, arrived at and were entangled in the 

 moving mass wdiich cooled as the axinitic pyroxenite at 

 the Coiebrook. The whole question of this occurrence of 

 axinite possesses a special interest for all occupied with 

 the prol)lems connected with the origin of igneous rocks. 



Microscopical inspection of the tourmaline-quartz-por- 

 phyry at the South Renison Bell mine discloses a ground- 

 mass existing as a Mosaic of quartz and tourmaline, which 

 contains por])hyritic crystals of quartz and nests of large 

 tourmaline and quartz crj'stals. There is no doubt as to 

 the tourmaline. Its colour is brow,nish yellow and ])lue, 

 often in one and the same crystal, strongly dichroic 

 O > E, axis of maximum elasticity || 0. The tourmaline 

 often enwraps grains of qtiartz. The quartz contains 

 vacuum bubbles in fluid inclusions in considerable 

 quantity. 



Last year a note on datholite as occurring in the Cole- 

 brook limurite was submitted by one of us to the society, (f) 

 and we hav^ since taken occasion to examine this mineral 

 microscopically. In thin section it is colourless, but in 

 polarised light the interference colours are high, comprising 

 the tints of the second and third orders of Newton's scale. 

 The double refraction is slightly under that of augite. In 



* Massige Gresteine. H. Rosenbusch, 1896, p. 103. 

 J Notes on some recently discovered and other minerals occurring in 

 Tasmania. W. F. Petterd. Proc. Roy. Soc. Tasm. 1897, p. 63. 



