Silicates


Non-Silicates Minerals Outline

The basic building block of the silicates is the silica tetrahedron. Each silicon atom is attached to four oxygen atoms by tetahedral bonds. This results in a 4- charge on the Si04 group.

There are many ways in which the SiO4 tetrahedra can be assembled to build neutral silicate mineral structures. These structures are the major rock-forming minerals.

  • Olivines and Garnets

    Isolated tetrahedra balanced by the cations magnesium (Mg), iron (Fe),calcium (Ca)

  • Pyroxenes

    Single chains of tetrahedra balanced by similar metal cations and sodium (Na)

  • Amphiboles

    Double chains of tetrahedra balanced by similar cations.

  • Micas and Clay Minerals

    Sheets of tetrahedra are the building blocks. Aluminum is also involved in these sheet structures which are charge-balanced by the cations Mg, Na and K.

  • Feldspars

    A second group of alumino-silicates, the tetrahedra form three-dimensional frameworks with Ca, Na and K as the balancing cations. The very abundant feldspar are subdivided in the K-Na bearing alkali feldspars and the Ca-Na solid-solution series called the plagioclase feldspars.

  • Quartz

    Silica tetrahedra alone can form a neutral three-dimensional framework structure with no need for other cations. This arrangement forms a very stable structure.


    Non-Silicates Minerals Outline
    (c) Department of Civil and Geological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada, S7N 5A9