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Geosciences LibreTexts Bonding and Mineral Properties

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    The nature of chemical bonding in minerals controls many properties. The table below makes some comparisons. Covalent bonds are stronger than ionic bonds, which in turn are stronger than metallic bonds. Consequently, covalent minerals are hard and tenacious, while metallic ones are usually not, and ionic minerals fall between. Melting temperatures follow a similar pattern (covalent compounds generally melt at the highest temperatures due to their stronger bonds), while solubility in water is greatest for ionic crystals (because of their weak bonds and easy ionization).

    Bond type also affects crystal symmetry. Both ionic and metallic bonds are nondirectional so bonding can occur equally in all directions. In contrast, covalent bonds involve pairs of atoms and are linear. Consequently, metallic and ionic minerals generally have high symmetry compared with covalent ones.

    Characteristics of Minerals Dominated by Different Kinds of Bonds
    property ionic bonds covalent bonds metallic bonds
    common elements involved from opposite sides of the
    Periodic Chart
    close together in the
    Periodic Chart
    transition metals
    electrical conductivity low low high
    thermal conductivity low low high
    solubility in water high low very low
    melting temperature moderate to high high variable
    hardness medium to hard very hard often malleable
    ability to break brittle, good cleavage brittle, common fractures variable
    crystal symmetry high symmetry low symmetry very high symmetry
    transparency fully to partially transparent partially transparent or opaque opaque
    how common? most nonmetallic minerals some minerals most metallic minerals
    examples halite (NaCl); calcite (CaCO3) diamond (C); sphalerite (ZnS) copper (Cu); silver (Ag)

    This page titled Bonding and Mineral Properties 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.