Question

what is the building unit of silicates?

Answer 1

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

Answer 2

The basic unit of silicate, [SiO4]4- tetrahedron, can form single and double chains and sheets.