A new method for fracturing mineral particles for cross-sectional FESEM analysis

Cross-sectional samples of mineral particles observed in a field emission scanning electron microscope (FESEM) can provide information on their shape, dimensions, and crystal growth that is difficult to obtain with other preparation methods and analytical techniques. A novel approach for the preparation and measurement of mineral particles in cross-section was investigated in this work. The unique sample preparation method involves vacuum embedding the mineral particles in epoxy and mechanically fracturing the mineral particles across their lengths. The morphology and characteristics of the particle cross-sections can be directly observed in a FESEM. The dimensions of the particle cross-sections can then be measured from the FESEM images off-line with a commercial software package. The procedure was used to characterize a chrysotile standard reference material, South African crocidolite and an amosite standard reference material. The major and minor cross-section chord lengths were recorded for 25 particles for each of the three samples. The chrysotile sample had average major and minor cross-section chord lengths of 0.06 mu m and 0.05 mu m, respectively. The South African crocidolite sample had average major and minor cross-section chord lengths of 0.09 mu m and 0.07 mu m, respectively. The amosite sample had average major and minor cross-section chord lengths of 0.23 mu m and 0.15 mu m, respectively. The chrysotile sample had the smallest cross-sectional chord measurements, while the amosite had the largest cross-sectional chord measurements. The average chord cross-section ratios of the major to minor chord lengths were 1.1 for chrysotile, 1.4 for crocidolite and 1.7 for amosite. The chord cross-section ratios illustrate that chrysotile has a nearly circular cross-section in comparison to crocidolite and amosite.