Silicate

I. Overview

Silicate minerals include all minerals containing silicates. These minerals are widely distributed in nature. There are more than 800 minerals found, accounting for one-third of the known minerals and accounting for 80% of the total weight of the earth's crust. They not only are three main types of rocks (igneous, metamorphic, sedimentary section) of the main rock-forming minerals, but also on industry, national defense important non-metallic mineral resources. Such as mica , asbestos , kaolinite, feldspar , talc and so on. In addition, a range of useful elements such as Be, Li, B, Zn, Rb, Cs, etc. can also be extracted from the silicate.

(1) Chemical composition

The main elements constituting the silicate mineral are: O, Si, Al, Fe, Ca, Mg, Na, K followed by Mn, Ti, B, Be, Zr, Rb, Cs, F and other elements. The elements constituting the silicate are mainly inert gas type ions, followed by transition ions, and the number of silicates composed of copper ions is small.

(2) Crystal structure

Although there are not many types of elements constituting silicate minerals, the number of minerals is very large, mainly due to the complicated internal structure and the existence of a wide range of similarities. In the silicate crystal structure, each silicon ion is surrounded by four oxygen ions, and four oxygen ions are distributed at the top of the four corners to form a silicon tetrahedron [SiO ₄ ] ^{4 +} , which is a silicate. The basic structural unit.

1. Island structure 2. Ring structure 3. Chain structure (including single chain and double chain) 4. Layered structure 5. Frame structure

(3) The same type of image

The substitution of isomorphisms in silicates is extremely common. Thereby the composition of the silicate is further complicated. The continuous isomorphic mineral series is common in silicates. As is well known, the plagioclase series is the same as the series; the olivine series. In addition to the existence of a wide range of equivalent and heterogeneous isomorphisms between cations, there is also a phenomenon of isomorphism between anions, such as [SiO ₄ ] ^{4 -} can be [PO ₄ ] ^3- or [SO ₄ ] ^2- instead; O, [OH] and F are replaced with each other.

(4) Chemical bonds

The chemical bonds of silicate minerals are mainly ionic bonds and covalent bonds. The interior of the complex anion formed by the silicon oxide is mainly a covalent bond, and the bond of the complex anion to the cation is an ionic bond. Layered silicate minerals still have molecular bonds.

The morphology and many physical properties of silicate minerals have obvious constraints on their internal structure. For example, the chain structure silicates are mostly columnar and needle-like; the layered silicate crystals are mostly plate-like and sheet-like. Shape, and a set of complete cleavage. It can be seen that the silicate structure can better reflect the essential characteristics of the silicate, so the silicate can be divided into the following five sub-categories according to the internal structure.

1. Island silicate subclass,

2. Cyclic silicate subclasses,

3. Chain silicate subclasses,

4. Layered silicate subclasses,

5. Frame silicate subclasses.