BY W. F. PETTERD, C.M.Z.S. 125 



225. NoSELiTE (Silicate of Aluminium and Sodiu7n, 

 with Sidphate of Sodium). 



This exceptionally rare mineral, as occurring in Aus- 

 tralia, is only known as a pseudomorph to limonite in the 

 elseolite-syenite of Mt. Livingstone, at Port Cygnet. 



In the elseolite-syenite porphyry of the same locality the 

 micro crystals may prove to be an analagous mineral, 

 known as hauyne. 



In both occurrences the minerals are practically micro- 

 scopic, and thsy can be det-ected in thin section under the 

 microscope scattered throughout the slide. 



*226. Obsidianites or Australites (Acid Meteorites). 



The remarkable small objects which have received the 

 above appellations are certainly not to be considered true 

 mineral species, but the general interest which has been 

 recently aroused respecting them, and the fact that they 

 are still from time to time unexpectedly occurring, princi- 

 pally in alluvial mine workings — in which case they are 

 generally the cause of much speculation as to their cause 

 and origin — must be accepted as the reasons for any refer- 

 ence to them in this Catalogue. Moreover, it is not by 

 any means unusual for these objects to be considered fit 

 subjects for elucidation by the mineralogist. 



In composition they may be taken as a true natural 

 glass, of an external dark — almost black — colour, but which 

 shows in the thinner portions and on the edges a trans- 

 lucent brown bottle-green colour. In form they may be 

 crudely classed as falling into four distinct types, viz., 

 those of a dumb-bell form, more or less contracted in the 

 middle, and often with a marginal groove or beading. In 

 size these rarely exceed 3 inches in length by about f-inch 

 across the spatulate ends. Secondly, those w^hich have 

 a discoidal form, often flat on one face and discoidal on 

 the reverse, with a marginal rim, which is occasionally 

 distinctly impressed on the extreme edge of the flatter 

 surface ; or this form may vary to bi-convex with a medial 

 fluted region. Thirdly, those which may be bung or 

 stopper-shaped, more often wider at one end than the 

 other, and altogether much m.ore bulky than the last- 

 mentioned. This is apparently the commonest form, 

 especially in certain localities in the West Australian 

 region. Lastly, those which affect an ovate outline, or 

 which may conveniently be termed elytron-shaped. These 

 are more or less rounded on either side, and but rarely 

 reach more than 2 inches in length by about |-inch in 



