NOTES ON A PLANT-HKAKINO OOMMON BLACK 

 0|>A[. FROM TWKKI) HEAOS. N.S.W. 



By ERNEST W. SKEATS, D.Sc, A.R.G.S., F.6.8. 



(Professor of Geology and Mineralogy, University of 

 Melbourne.) 



{Read before the Royal Soeiety of Queensland, April 21th, 



1914.) 



Introduction. 



About two years ago, Mr. H. C. Richards, M.Sc, 

 Lecturer in Geology at the University of Queensland, 

 sent me some fragments of a dense black, hard material, 

 which he found associated with the basalt flows of Tweed 

 Heads, New South Wales. Mr. Richards quite naturally, 

 from its appearance and occurrence, described it to me as 

 tachylyte, and as forming the glassy selvage to a basic 

 lava flow. I concurred in the indentification, but at the 

 time had no occasion to test it critically. Towards the 

 end of the year 1912, however, I had occasion to determine 

 its specific gravity, and that of some tachylytes from 

 Victoria and elsewhere. To my surprise I found that it 

 differed entirelj^ in its properties from tachyl^^e. 



Geological Occurrence. 



The mode of occurrence of the material will l>e seej. 



fiom the sketch section, from information kindl}^ supplied 



by Mr. Richards. The basalt of Tweed Heads was the 



subject of a short note by Mr. E. C. Andrews, B.A., in the 



