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6.1: Cleavage

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    Cleavage is the splitting of a gemstone along the direction of its crystal faces where atoms have weaker bonding. This can occur only in crystalline minerals when a precise blow is given in a particular direction. The result of cleavage is a more or less flat plane with often a silky luster.
    Cleavage is a reproducible property of a gemstone and can be done at any point of the cleavage direction.

    There are several directions of cleavage.

    • Prismatic cleavage
    • Basal cleavage
    • Pinacoidal cleavage
    • Octahedral cleavage
    • Rhombohedral cleavage

    The quality of cleavage is expressed with a few simple phrases.

    • Perfect
    • Good (or imperfect)
    • Fair (or moderate)
    • Poor (or weak)
    • None

    File:Cleavage prismatic.jpg

    Figure \(\PageIndex{1}\): Prismatic cleavage

    File:Cleavage basal.jpg

    Figure \(\PageIndex{2}\): Basal cleavage


    Stones and their cleavage directions:

    Table \(\PageIndex{1}\)

    Cleavage Directions Stones Quality
    Basal 1 Topaz Perfect
        Beryl Imperfect
    Prismatic 2 Peridot Perfect
        Spodumene Perfect
        Chrysoberyl Weak to Moderate
        Diopside Perfect
    Cubic 3 Halite Perfect
    Rhombohedral 3 Calcite Perfect
        Rhodochrosite Perfect
    Octhahedral 4 Fluorite Perfect
        Diamond Perfect
    Dodecahedral 6 Sphalerite Perfect

    Sources

    • Gemmology 3rd edition (2005) - Peter Read

    This page titled 6.1: Cleavage was last modified on Fri, 06 May 2022 23:29:17 GMT and is shared under a CC BY-NC-SA 2.5 license and was authored, remixed, and/or curated by gemology via source content that was edited to the style and standards of the LibreTexts platform.

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