Mineral matter hydrogen bonding

Figure 3.4a shows a projection of a 1 1 layer silicate oriented with the octahedral sheet uppermost. Note that the hydrogen atoms are shown as small circles bonded to the oxygen atoms of the hydroxyl groups. Rather than terminate the external plane of oxygen atoms of the octahedral sheet by hydroxyl groups, as in the 1 1 minerals, it is possible to add a second tetrahedral sheet, this one inverted with reference to the first tetrahedral sheet, making a 2 1 mineral structure. Here the 2 refers to the number of tetrahedral sheets and the 1 refers to the number of octahedral sheets. This type of mineral is shown in Figure 3.4, also in projection. Finally, there are layer structures which have octahedral (hydroxide) sheets inserted between 2 1 type layers. These are labeled 2 1 1 (see Figure 3.4c). Clearly, as the complexity of the layer increases, the thickness of the layer also increases. Since this thickness is easily measured by a simple X-ray diffraction experiment, the identity of the layer t fpe is a trivial matter.

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