Indexing asymmetrical Laue photographs: application to echinoid calcite

Recent computer methods of indexing asymmetrical Laue photographs of unaligned crystals are briefly reviewed, and a new, more efficient, algorithm programmed in Basic for a minicomputer is described. The interactive programs will index symmetrical or asymmetrical (no photograph symmetry is used) transmission or back-reflection Laue patterns of any crystal. A least-squares method of determining crystallographic directions from Laue data is also described. Typical results of the application of these methods to all crystal systems are presented. Zones with indices as high as eight and spots with Miller indices as high as 24 have been identified in back-reflection photographs of echinoid (sea-urchin) calcite.