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Jai Ganesh

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Registered: 2005-06-28

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Silica

Silica

Gist

Silica is the common name for silicon dioxide (SiO2), a naturally occurring mineral composed of one silicon and two oxygen atoms. It is the most abundant mineral in the Earth's crust, found in sand, granite, and rocks, and is used in a wide array of products including glass, concrete, and electronics. Silica is generally safe but can be a choking hazard, and inhaling fine airborne dust from certain industrial activities can lead to serious lung diseases like silicosis. 

Silica is used in a wide range of applications, including glass manufacturing, construction (cement, concrete), electronics (semiconductors, microchips), and industrial processes like water filtration and chemical manufacturing. It also functions as a common food additive, a desiccant in moisture-absorbing packets, and a component in products like pottery, ceramics, and even some cosmetics and supplements.

Summary

Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO2, commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product. Examples include fused quartz, fumed silica, opal, and aerogels. It is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored.

Silicon dioxide is a common fundamental constituent of glass.

Natural occurrence:

Geology

SiO2 is most commonly encountered in nature as quartz, which comprises more than 10% by mass of the Earth's crust. Quartz is the only polymorph of silica stable at the Earth's surface. Metastable occurrences of the high-pressure forms coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism. The high-temperature forms of tridymite and cristobalite are known from silica-rich volcanic rocks. In many parts of the world, silica is the major constituent of sand.

Biology

Even though it is poorly soluble, silica occurs in many plants such as rice. Plant materials with high silica phytolith content appear to be of importance to grazing animals, from chewing insects to ungulates. Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by insects may have developed as a defense mechanism against predation.

Silica is also the primary component of rice husk ash, which is used, for example, in filtration and as supplementary cementitious material (SCM) in cement and concrete manufacturing.

Silicification in and by cells has been common in the biological world and it occurs in bacteria, protists, plants, and animals (invertebrates and vertebrates).

Prominent examples include:

* Tests or frustules (i.e. shells) of diatoms, Radiolaria, and testate amoebae.
* Silica phytoliths in the cells of many plants including Equisetaceae, many grasses, and a wide range of dicotyledons.
* The spicules forming the skeleton of many sponges.

Details

Also called silica sand or quartz sand, silica is silicon dioxide (SiO2). Silicon compounds are the most significant component of the Earth’s crust. Since sand is plentiful, easy to mine and relatively easy to process, it is the primary ore source of silicon. The metamorphic rock, quartzite, is another source.

Silicon (Si) is a semi-metallic or metalloid, because it has several of the metallic characteristics. Silicon is never found in its natural state, but rather in combination with oxygen as the silicate ion  in silica-rich rocks such as obsidian, granite, diorite, and sandstone. Feldspar and quartz are the most significant silicate minerals. Silicon alloys include a variety of metals, including iron, aluminum, copper, nickel, manganese and ferrochromium.

Description

Also called silica sand or quartz sand, silica is made of silicon dioxide (SiO2). Silicon compounds are the most significant component of the Earth’s crust. Since sand is plentiful, easy to mine and relatively easy to process, it is the primary ore source of silicon. The metamorphic rock, quartzite, is another source.

Silicon (Si) is a semi-metallic or metalloid, because it has several of the metallic characteristics. Silicon is never found in its natural state, but rather in combination with oxygen as the silicate ion - in silica-rich rocks such as obsidian, granite, diorite, and sandstone. Feldspar and quartz are the most significant silicate minerals. Silicon alloys include a variety of metals, including iron, aluminum, copper, nickel, manganese and ferrochromium.

Relation to Mining

In almost all cases, silica mining uses open pit or dredging mining methods with standard mining equipment.  Except for temporarily disturbing the immediate area while mining operations are active, sand and gravel mining usually has limited environmental impact.

Uses

Ferrosilicon alloys are used to improve the strength and quality of iron and steel products. Tools, for instance, are made of steel and ferrosilicon.

In addition to tool steels, an example of “alloy steels,” ferrosilicon is used in the manufacture of stainless steels, carbon steels, and other alloy steels.  An alloy steel refers to all finished steels other than stainless and carbon steels. Stainless steels are used when superior corrosion resistance, hygiene, aesthetic, and wear-resistance qualities are needed.

Carbon steels are used extensively in suspension bridges and other structural support material, and in automotive bodies, to name a few.

Silicon is used in the aluminum industry to improve castability and weldability. Silicon-aluminum alloys tend to have relatively low strength and ductility, so other metals, especially magnesium and copper, are often added to improve strength.

In the chemicals industry, silicon metal is the starting point for the production of silianes, silicones, fumed silica, and semiconductor-grade silicon. Silanes are the used to make silicone resins, lubricants, anti-foaming agents, and water-repellent compounds. Silicones are used as lubricants, hydraulic fluids, electrical insulators, and moisture-proof treatments.

Semiconductor-grade silicon is used in the manufacture of silicon chips and solar cells. Fumed silica is used as a filler in the cement and refractory materials industries, as well as in heat insulation and filling material for synthetic rubbers, polymers and grouts.

Silica is used in ceramics and in making glass.

Silicon is considered a semiconductor. This means that it conducts electricity, but not as well as a metal such as copper or silver. This physical property makes silicon an important commodity in the computer manufacturing business.

Additional Information

Silica is a compound of the two most abundant elements in Earth’s crust, silicon and oxygen, SiO2. The mass of Earth’s crust is 59 percent silica, the main constituent of more than 95 percent of the known rocks. Silica has three main crystalline varieties: quartz (by far the most abundant), tridymite, and cristobalite. Other varieties include coesite, keatite, and lechatelierite. Silica sand is used in buildings and roads in the form of portland cement, concrete, and mortar, as well as sandstone. Silica also is used in grinding and polishing glass and stone; in foundry molds; in the manufacture of glass, ceramics, silicon carbide, ferrosilicon, and silicones; as a refractory material; and as gemstones. Silica gel is often used as a desiccant to remove moisture.

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