PAPERS, 1897. 



ON THE 

 OCCURRENCE OF LIMURITE IN TASMANIA. 

 By W. H. Twelvetrees, F.O.S., and W. F. Petterd, 



C.M.Z.S. 



Bead May 4, 1897. 



Limurite (Frossard), described by F. Zirkel (N. Jahrbuch 

 fiir Mineralogie, 1879). 



This peculiar and interesting rock occurs in considerable 

 quantity at North-east Dundas, on the property held under 

 mineral lease by the Colebrook Prospecting Association 

 (Section 216, 93m). It apparently consists of a huge contact 

 mass, which is of an irregular lenticular form, being bounded 

 on its eastern side by a hard dark-coloured metamorphic 

 slate, probably of silurian age, and on the western side 

 wholly or partially by green serpentine, which is in places 

 much decomposed. 



So far as known, no granite rock exists in immediate con- 

 nection with its occurrence, but such acidic rocks are 

 abundant within a comparatively short distance. By the 

 decomposition of the rock itself, as well as of the iron-bearing 

 ores it contains, the actual outcrop of the mass has been con- 

 verted to a gossan material, which projects with extreme 

 irregularity above the surface of the enclosing rocks, after 

 the form of a laccolite. Samples of the rock broken from, 

 beneath its outer crust present a very attractive appearance 

 and show clearly the violet-coloured mineral axinite in 

 extremely well-formed oblique rhombohedral plates, which 

 are almost tabular, the browner augite and milk-white calcite 

 with occasional patches of actinolite. 



Macroscopically the axinite is found in large lustrous 

 crystal masses, the individual crystals often reaching half an 

 inch in length, thus forming specimens of great interest to 

 the mineralogist. The augite is also in large crystals, but 

 scarcely distinguishable from the more abundant axinite. 

 The calcite is at times obtained in somewhat large masses, in 

 which are often imbedded isolated crystals of axinite, which 

 can be readily freed from the matrix by digestion in acid. 

 The actinolite varies from felted aggregations of microscopic 

 size to radiating collections of blades, occasionally some 

 inches in length, in the latter case presenting unusually fine 

 examples of the species. Various metallic minerals are found 

 as accessory constituents, of which pyrrnotite is apparently 



