Sentence:  For example , there are persons who are in physical science , in the field of mineralogy , trained in crystallography , who use only X-rays , applying only the <WSD>powder</WSD> technique of X-ray diffraction , to clay minerals only , and who have spent the last fifteen years concentrating on the montmorillonites ; or persons in the social sciences in the field of anthropology , studying the lung capacity of seven Andean Indians . 
Meaning of the word marked with <WSD> tags:  a process for identifying minerals or crystals; a small rod is coated with a powdered form of the substance and subjected to suitably modified X-rays; the pattern of diffracted rings is used for identification