GEOLOGICAL, MINERALOGICAL, CER.43IIC APPLICATIONS 



y uniform grading good radiographs 

 were obtained. Figs. 9 and 10 show taiUngs 

 from a lead ore which were examined to 

 assess the vahie of re treatment. The material 

 consisted of fine transparent or translucent 

 grains all more or less heavilj^ iron stained. 

 The valuable minerals were cerussite and 

 mimetite, and these were almost indistin- 

 guishable from gangue minerals such as cal- 

 cite, other carbonates, c^uartz, etc., because 

 of the fine grain size iron staining and the 

 general weathered condition of the material. 

 The radiograph clearly shows the lead-bear- 

 ing particles (white); assaying by particle 

 counting was fairly easy on the radiograph 

 but quite impossible directly on the sample. 

 For example, a large irregular grain near the 

 center of the field appears quite uniform but 

 reference to the radiograph shows it to con- 

 sist of almost equal amounts of gangue and 

 lead mineral. 



Fig. 11 shows a radiograph on gold ore 

 tailings which shows the state of association 

 of the gold. For example, some of the gold 

 particles are free from gangue and should not 

 have passed the concentration process. 

 Others are associated with gangue and clearly 

 could be recovered by further grinding and 

 separation but the very fine dissemination of 

 particles visible in some of the grains are 

 clearly beyond the possibilities of physical 

 separation methods. Distinguishing gold 

 from accompanying pyrite is difficult opti- 

 cally and the radiograph offers a much better 

 chance of detecting the odd grain or fine 

 disseminations which are responsible for 

 tailing losses. 



The application of radiography to opaque 

 materials is further exemplified by reference 

 to investigations on the structure of sin- 

 tered iron ores. Figs. 12 and 13 show radio- 

 graphs of some sintered ore at different 

 magnifications. The material is very hetero- 

 geneous but mainly consists of iron oxides 

 embedded in a melilite tjqje silicate. The ir- 

 regular distribution of voids and pools of 

 solidified silicate can be seen. Pin-point 



x-ray diffraction analysis on the area in Fig. 

 13 showed the dendrites to be FeO grown 

 from an iron-monticellite type silicate, 



Fig. 9. Optical micrograph of lead ore tailings. 

 X113 



Fig. 10. Microradiograph of same area as Fig. 

 9 showing lead distribution (white). X113 



577 



