Not all X-ray machines are shaped like dental X-ray machines. Sedimentologists use a high-powered, commercially available version that completely encloses the sample and film in an oven-like, lead-lined box. Film is available in many standard sizes, and in many kinds adapted to different uses, but ordinary medical films should work well for shells. Because of the need for heavy lead lining (in the box or in an apron), the machines are hardly portable. Arnold Bouma included a chapter on the geologic uses of X-rays in his book on sedimentologic techniques, with many pointers that could only have been gained by experience. I'll look up the reference if people are interested. It's not the kind of thing that most people would want to set up in the home. If I may make a suggestion: One of Conch-L's dealers could supply one of our medical conchologists with examples of fake shells for X-raying. This would make a really interesting set of images for publication. As to guavas <sigh>, they are a favorite of mine, though they are not often available here and I usually content myself with guava jam instead. The flavor is complex and subtle, and there are many kinds. But some tropical fruits have surprising vernacular connotations <wink> and I was wondering what extra meanings, if any, Emilio intended. After "conchas," I have learned that one must choose one's words carefully in Latin America. And on Conch-L. <grin> Andrew K. Rindsberg Geological Survey of Alabama Tuscaloosa, Alabama, USA (warm at 33 N latitude, but not tropical)