The regular, orderly, periodic or repeated arrangement of atoms, molecules, or ions in a crystal.
See Alexandrite Tsarstone collectors guide, Definition of Crystal structure formation, http://m.alexandrite.net/viewpage.html?id=GG-088-00011 (The regular, orderly, periodic or repeated arrangement of atoms, molecules, or ions in a crystal.) (as of Apr. 03, 2026, 14:12 GMT).