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13: Crystal Structures

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    Figure 13.1: The atomic arrangements in quartz and sodalite


    • The development of X-ray diffraction techniques allowed mineralogists and chemists to directly investigate the nature of crystal structures.
    • Minerals have highly ordered and repetitive atomic arrangements.
    • We can model many crystal structures as being spherical atoms held together by ionic bonds.
    • Ionic crystals contain anions packed around cations and vice versa.
    • The key controls on ionic bonds are ionic size and charge.
    • An atom’s coordination number is the number of other atoms that it bonds to.
    • Most common cations bond to 3, 4, 6, or 8 anions; alkalis and other large ions bond to more.
    • The strength of an ionic bond is an ion’s charge divided by its coordination number.
    • Atoms pack tightly together in some minerals; in others, atoms are in networks with geometric shapes.
    • Compositional variations in silicate minerals are directly related to the nature of the crystallographic sites in their structures.

    This page titled 13: Crystal Structures is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Dexter Perkins via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.