The original description of aramayoite by Spencer in 1926 contained only a qualitative discussion of the crystallography, because suitable crystals for a more rigorous treatment were not found. The pseudo-tetragonal symmetry was recognized, and cleavages were noted, but only one was defined. Twinning was later observed in polished section by Schneiderhöhn and Ramdohr, but undefined. Yardley demonstrated the triclinic symmetry of aramayoite by the Laue method, and determined the spacings of a considerable number of planes in the crystal. From these data she formulated a unit cell and correlated the X-ray data with Spencer's crystallographic results.

Several specimens of aramayoite found in our recently acquired Ahlfeld Bolivian collection contained small but excellent crystals. Measurement of these indicated that the Yardley X-ray crystallography was not consistent with an adequate morphological treatment of the form-development. The twenty-seven forms found by us lead to an obvious crystallographic unit (fig. 1), bearing a rather complex relationship to the Yardley unit. In order to test the suitability of the latter, we repeated the X-ray examination by the modern Weissenberg method and found complete accordance with our morphological treatment, as will be shown below.