Structure determination of plagioclase (Labradorite): I. Al/Si distribution in an An66 (neutron diffraction): II. Superstructure of an An54 (X‐ray diffraction)

The Al/Si distribution in a plagioclase An66 was determined using neutron diffraction. According to the results of neutron experiments and the extended theory of satellites the superstructure of an An54 was determined. The final R‐value is 4.7% for all over 2540 reflections (Ra‐ref.=2.8% and Re‐ref.=21.4%).