Geology Reference
In-Depth Information
Multiple tetrahedra combine to form silicate structures, which are then held together
with atoms of other elements, such as iron, magnesium, potassium, sodium, and calci-
um.
The chemical composition and structure of a silicate mineral provide clues to
the temperature and pressure conditions under which it was formed. Many silic-
ate minerals form from the cooling of molten rock (magma, described in Chapter
7). Others form under the pressure of mountain building (see Chapter 9) or as sur-
face materials are weathered (see Chapter 7).
Finding silicates in many shapes
The different silicate structures are created by the way multiple silicon-oxygen tetra-
hedra combine to share oxygen atoms. Five common silicate structures exist:
Single tetrahedral: Individual tetrahedra that are held together by other elements
without sharing any oxygen atoms have the single tetrahedral structure, as illus-
trated in Figure 6-5. The mineral olivine has single tetrathedral structure.
Single chains: In single chain silicates, the tetrahedra share an oxygen atom with
two other tetrahedra, forming a linked chain as illustrated in Figure 6-6. The miner-
al augite has a single chain silicate structure.
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