BY W. H. TWELVETREES. 43 



a rock composed of the dark silicates in a gronndmass of 

 analcime. Some authors affirm the analcime to be Primary, 

 others believe it may be the hydration product of original 

 glass. 



I'he essexite of the Regatta ground is a dark dioritic-look- 

 ing rock found at the water's edge below the Regatta Box. 

 I have also seen it at Oyster Cove. It consists of labradorite 

 and andesine felspars + augite + amphibole with quartz 

 and iron oxide. Although it possesses the characteristics of 

 its family, it differs, according to Professor Rosenbusch, in 

 type from other essexites known to him, and requires further 

 study. 



The jacupirangite (nepheline + augite) is not always so 

 intensely pyroxenic as typical specimens from Jacupiranga. 

 Professor Rosenbusch has, with his usual kindness, fur- 

 nished me w^ith the following note upon it. 



" It is a highly pyroxenic differentiation of the elasolite 

 and alkali syenites at the Regatta ground, Port Cygnet, and 

 possesses the characters of the so-called jacupirangite of 

 San Paulo, in Brazil, and of Alno, in Sweden. It would be 

 rather interesting to examine the sand of any adjacent creeks 

 which may flow over the syenites with this jacupirangite 

 facies. The interesting mineral, Baddeleyite (Zr Oo) may 

 be expected to occur." 



Further south from this promontory a few dykes were 

 visited on the shore of the Arm, |tra versing mudstones of 

 Permo-Carboniferous age. One is a green solvsbergite 

 porphyry, its colour due to aegirine. It contains parallel 

 layers of porphyritic tabular crystals of sanidine. Another 

 dyke, a little further south, contains the new variety of 

 garnet, Johnstonotite. It is a mica solvsbergite. Professor 

 Rosenbusch calls attention to an undetermined mineral 

 which he has observed in it. He says . — 



" This rock contains in small quantities, but widely dis- 

 tributed, a strongly refractive, red, transparent, isotropic 

 mineral, which I have noticed in many other rocks of the 

 alkali series, but which I have not been able to determine 

 yet. I suspect that it belongs to the pyrochlore group." 



The next day the party visited Mount Livingstone, one 

 mile N.E. of Lovett, where large collections were made of the 

 beautiful elaeolite syenite porphyry, which seems to form 

 the axis of the hill, and can be gathered in loose blocks on the 

 crest. These rocks had been previously designated phono- 

 litic trachyte and nosean or hauyne trachyte by the writer, 

 but Professor Rosenbusch has identified them as elaeolite 

 syenite porphyries with trachytoid groundmass. He has 

 taken the trouble to accompany his identification with the 



