129 



few small grains of apatite were noticed. The rock must be 

 classed as a mica diorite. 



Perhaps the most unusual type of rock in Aldgate is 

 represented by a specimen obtained from a vein near the 

 road leading up to the Stirling East schoolhouse. It is com- 

 posed entirely of quartz and tourmaline in a kind of graphic 

 intergrowth. (See plate iii., fig. 6.) The tourmaline occurs 

 quite anhedrally, is violet-brown, and very strongly pleo- 

 chroic. The quartz grains are rounded, somewhat strained, 

 and very full of cavities, which are often clouded by the de- 

 position of a red material, probably haematite. The clear 

 cavities by their comparatively low relief would be probably 

 filled with water. This rock would be best classed as a tour- 

 maline quartz pegmatite. 



Mr. Howchin informs me he has found other instances 

 of it in the erratics in the Permo-Carboniferous glacial de- 

 posits at Black Swamp, a new locality for glacial beds of 

 this age, between Strathalbyn and Goolwa. 



V. Tankalilla. 



The Yankalilla rocks of this series occur in Sections 1186 

 and 1187, of the Hundred of Yankalilla. They vary to a 

 large extent in character, but though only a few slides have 

 been examined, there is little doubt of their origin from the 

 parent magma of the Aldgate-Houghton rocks. 



Slide No. 588 is of a granite composed originally of 

 diopside, quartz, orthoclase, plagioclase, sphene, apatite, and 

 magnetite, probably titaniferous. It has now suffered vari- 

 ous alterations. The quartz is very strained and partially 

 shattered. The diopside has become partly uralitized and 

 faintly pleochroic, but in the main its change is to epidote 

 in large green grains, present in very large amount. The 

 magnetite is slightly altered to haematite. The texture is 

 granitic, slightly altered by crushing. 



Slide 598 is composed of orthoclase and microcline, with 

 diopside partially uralitized, epidote, quartz, sphene, and 

 apatite, together with a sprinkling of haematite. This is obvi- 

 ously a syenite. 



Other sections from this locality are in general similar 

 to 598, differing only in the occurrence of leucoxene and the 

 presence of a few plagioclase crystals. 



vi. The Gorge, South of Normanville. 



Several specimens were obtained of rocks of the Aldgate- 

 Houghton magma, which may be briefly described. 



No. 596 is a granodiorite, containing as the predominant 

 mineral very dusty albite, together with a much smaller 



