Specific gravities of lunar materials using helium pycnometry

An existing technique, helium pycnometry, has been adapted for the measurement of specific gravities of lunar samples, where surface areas are low (less than 1 sq m/g) and crushing the sample to a fine powder is highly undesirable. The technique is superior to typical liquid immersion methods, in that it is noncontaminating and, where vuggy or porous samples are concerned, should provide a more accurate (higher) absolute density value. The experimental helium pycnometry measurements have been compared in three instances for two rocks with values calculated from a normative mineral composition. The comparison appears good, however, where differences occur, the direct experimental technique appears to provide the better value and to be capable of indicating density variations within a single rock sample.