2 SUPPLEMENTARY NOTE ON LIMURITE XN TASMANIA. 



granite area to the west is shown ])y the tourmaline and 

 axinite ju.st alluded to, and if these vapours extended to 

 the pyroxenic magma at the Colebrook, and were carried 

 up with it, the origin of the limurite rock would be ac- 

 counted for. J^ast year a Note on Datholite was sal)mitted 

 by Mr. W. F. Petterd, and now the authors state the results 

 of a microscopical examination of this mineral. Another 

 new mineral is added to the list of the components of this 

 singular rock, viz., the boro-calciuni silicate, danburite, and 

 its microscopical characters are enumerated. A further 

 mineral with characters suggestive of its being a precipitate 

 from, a boric solution is mentioned. It is somewhat similar 

 to the decomposition ijroduct of boracite known as parasite, 

 a hydrous magnesian borate. The authors consider that 

 the limurite rock throws light on the question of the age 

 of the granite on the West Coast, as the Colebrook intru- 

 sion appears to be younger than the sei'pentinous and 

 :gab])roid rocks to the w^est of the mine. 



