Silica is a raw material for manufacturing glass, quartz glass, water glass, optical fiber, important parts of the electronics industry, optical instruments, handicrafts and refractory materials, and an important material for scientific research.

Uses of silica: plate glass, glass products, foundry sand, glass fiber, ceramic color glaze, sandblasting for rust prevention, sand for filtering, flux, refractories and the manufacture of Autoclaved Lightweight Concrete. Silica has a wide range of uses. The rare crystals in nature can be used to manufacture important parts, optical instruments and handicrafts in the electronics industry. Silica is an important raw material for manufacturing optical fibers. Generally pure quartz can be used to make quartz glass. Quartz glass has a very small expansion coefficient, equivalent to 1/18 of ordinary glass. It can withstand drastic changes in temperature and has good acid resistance (except HF). Therefore, quartz glass is often used to make high temperature resistant chemical instruments. Quartz sand is often used as glass raw materials and building materials.

Physical and chemical properties:
Silica is also called silica, with the chemical formula SiO₂. There are two kinds of crystalline silica and amorphous silica in nature.
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Crystalline silica is divided into three types: quartz, tridymite and cristobalite due to its different crystal structure. Pure quartz is a colorless crystal, and large and transparent prismatic quartz is called crystal. If the crystals with trace impurities have different colors, there are amethysts, citrines, smoky crystals and so on. Ordinary sand is fine quartz crystals, including yellow sand (more iron impurities) and white sand (less impurities and purer). In silicon dioxide crystals, the 4 valence electrons of silicon atoms and 4 oxygen atoms form 4 covalent bonds. The silicon atom is located in the center of the regular tetrahedron, and the 4 oxygen atoms are located on the 4 corners of the regular tetrahedron. Many These tetrahedrons are connected by oxygen atoms at the top corners, and each oxygen atom is shared by two tetrahedrons, that is, each oxygen atom is combined with two silicon atoms. SiO₂ is the simplest formula that expresses the composition, and it only expresses the ratio of the number of silicon and oxygen atoms in the silicon dioxide crystal. Silica is an atomic crystal.

The bond energy of the Si—O bond in SiO₂ is very high, with high melting point and boiling point (melting point 1723°C, boiling point 2230°C). The refractive index is approximately 1.6.

The refractive index of various silica products is: quartz sand is 1.547; powder quartz is 1.544; vein quartz is 1.542; diatomaceous earth is 1.42 to 1.48; fumed silica is 1.46; precipitated silica is 1.46.

The diatomaceous earth that exists in nature is amorphous silica, which is the remains of lower aquatic plant diatoms. It is a white solid or powder, porous, light, and soft solid with strong adsorption.