114, Dr. R. F. Rand — Some Transvaal EvKptires. 



a crystal ; their extension is attended by a change in the orientation 

 of the axes of elasticity of the felspar. As accessories, a few small 

 zircons are to be seen. 



No. 22. An irregular intrusion in the Magaliesberg Series, nortb . 

 of the Van der Merwe Eailway Station, Pretoria-Delagoa Bay line. 



Meg. A holocrystalline rock of grey colour and fine grain. 

 Sp. gr. 2-69. 



Mic. Shows interlacing bars of a greatly decomposed plagioclase 

 interwoven with a rhombic pyroxene, which is mostly altered into 

 bastite. The meshes of this framework are occupied by a micro- 

 graphic intergrowtli of quartz and semi-opaque felspar, the quartz 

 preponderating. Some magnetite occurs, and hornblende, sparingly. 

 A small vein traversing the section is filled with calcite. 



No. 23. — Locality : dyke in the Magaliesberg Series, north of Van 

 der Merwe Railway Station. 



Meg. Has a general likeness to No. 22, but is of somewhat 

 coarser grain. Sp. gr. 2-83. 



Mic. There is a framework of decomposed plagioclase, with 

 rhombic pyroxene as in No. 22, also much quartz in micrographic 

 intergrowth with felspar. In addition there is pale augite partly 

 altered into uralitic hornblende, and plentiful large flakes of 

 ilmenite partly decomposed into leucoxene. Patches of serpentine 

 occur as results of complete decomposition of rhombic pyroxene. 



Note. — In no Transvaal instance has the writer observed the 

 violent tingeing of augites so frequently seen where augite is 

 associated with titanium-bearing ores. 



No. 24. — Locality : dyke in the Magaliesberg Series, north ^of 

 Van der Merwe Railway Station. 



Meg. A bluish-black rock, of medium grain, partly crystalline. 

 Scratches under the knife. Sp. gr. 3. 



Mic. The rock consists of olivine, enstatite, and augite. The 

 olivine is for the most part serpeutinized ; the decomposition is of 

 the usual type along the cleavage-cracks. The serpentine is 

 greenish, sometimes showing a reddish iron-staining. Where the 

 augite shows change it is in the shape of an advancing cloudiness. 

 The enstatite is fairly fresh, but shows a little of the usual bastitic 

 alteration. Octahedra of magnetite occur. There are also a few 

 flakes of biotite ; and, quite rarely, narrow laths of plagioclase. 

 The rock is interesting as an example of the ultra-basic type. 



Vicinity of Klerhsdorp. 



Locality : ten miles north of Klerksdorp, Intrusive mass 

 occupying the floor of a broad valley between two sedimentary 

 series, usually regarded as being of Witwatersrand age. _ J^r-l.T.ijI 



No. 25. — Meg. A holocrystalline rock of fine grain. Dark-grey 

 in colour. Sp. gr. 2-96. 



Mic. Shows numerous plagioclase crystals of small and medium 

 size, among which are disposed fairly large crystals of augite, light 

 yellowish-brown in colour, twinned and herring-boned ; also, larger 

 irregularly -shaped crystals of enstatite ; neither augite nor enstatite 



