Powdered samples for x-ray analysis are often ground in mills by using a rotating ring and puck inside a grinding cylinder. Such commercial grinders are the Disc Mill (Angstrom, Inc.), Bleuler Mill (Applied Research Laboratories, Inc.), and Shatter-box (Spex Industries, Inc.). A grinding aid is frequently added along with the sample to increase the grinding efficiency, to minimize contamination caused by abrasion with the grinding media, and to eliminate sample’s sticking to the grinding surfaces and thus aid in sample transfer. Grinding aids frequently employed are soap powders, sodium alkylsulfonate, and Boraxo. These products contain sodium; this precludes their use when sodium is to be determined. Sterotex powder,1 a vegetable-fat product that is free of the elements determined by x-ray, has been tested and used as a grinding aid. Sterotex, a fine powder about 95% −200 mesh, easily and uniformly disperses with the sample. When required, it can be premixed with the sample to minimize spot-impacting of the sample on the grinding surfaces. To eliminate this problem with, for example, Boraxo, the as-received product should be ball-milled to about −50 mesh. Sterotex also imparts some binding action when briquets are prepared from the pulverized sample.