108 A METEORITE FROM ZULUI-AND. 



'>,_, Phosphorus 057 %. 



Akiminium trace. 



Magnesium trace. 



Platinum trace. 



Chlorine trace. 



Manganese not detected. 



Cobalt not detected. 



Chromium not detected. 



Obviously, with a body of such heterogenous structure, it 

 would be almost impossible to obtain an accurate sample of the 

 whole from one place only, and the above results may not there- 

 fore represent accurately the composition cf the whole body. 



For the examination of the internal structure, a small slice 

 (2y X 20 mm^ was cut from the corner where the sample had 

 been taken, ground flat, taking precautions against overheating, 

 and finely polished. 



At this stage the crystalline structure became apparent, 

 owing to the varying hardness of the several constituents, but it 

 was developed further by a brief immersion in dilute nitric acid, 

 as usual in metallographic investigations of the internal struc- 

 ture of steels. It then presented the appearance shown in 

 photograph No. 6. 



\\'hen examined under the microscope and its appearance 

 compared with published descriptions of other meteorites, some 

 difficulty was experienced in identifying the various constituents, 

 but this was found to be largely due to the use of vertical illumin- 

 ation instead of oblique. The difference produced in the appear- 

 ance in this manner is shown in photos No. 7 ( oblique ) and 8 

 (vertical), the dark constituent (taenite?) in one becoming the 

 white constituent in the other. 



Photograph No. 6 was taken with oblique illumination. 

 The long "bars" or "beams" which make up tlie greater 

 portion of the area of the section appear from their colour an i 

 structure to be most probably " kamacite," of lengths from about 

 2 to 8 mm, and widths in the neighbourhood of i mm ( excep- 

 tionally .5 and 1.5 mm). 



Surrounding these almost completely in nearly every case 

 are what appear to " combs " of taenite," and in between are 

 " fields " apparently of " plessite." 



The names given and used here are in accord with most of 

 the descriptions of structures, and some of the compositions, 

 given by different authors in the limited literature of the subject 

 available in Johannesburg. 



But with regard to the chemical compositions there appear 

 to be conflicting views. 



Kamacite is variously stated to be a solid solution with 6 to 

 7 % Nickel, and a chemical compound Te^iNi (Nickel 7 %). 



Taenite similarly is given as a solid solution containing 15 

 to 35 % Nickel, and also as a compound F„Ni (Nickel 15 %), 



