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Crystalline silica is a chemical compound found in all regions of the Earth, commonly used in manufacturing, glass production, and construction. It can cause silicosis if inhaled, so caution is necessary.
Crystalline silica is the scientific name for a chemical compound, SiO2, which is found in all regions of the Earth and in all layers of the geological record. It has been used in many industries for thousands of years, dating back to ancient Egypt. The most common form of crystalline silica is quartz.
Silica should not be confused with silicon, silicates or silicone. Silicon is the element Si, which together with oxygen makes up silica. Silicon is the second most abundant element on earth, after oxygen. Silicates are also formed by combining silicon and oxygen, but also include a metal in their chemical composition. Silicones are polymers, synthetic compounds.
Viewed in two forms, silica can be crystalline or amorphous. For silica to be crystalline, its molecules must be arranged in a repeating three-dimensional pattern. Amorphous silica does not have a crystalline structure. Opals are a type of non-crystalline silica.
Because it is polymorphic, crystalline silica can be found in more than one state. There are seven polymorphs, or forms, of SiO2. Four of these types are extremely rare. The other three – quartz, cristobalite and tridymite – are commonly found.
Quartz also has two states, alpha and beta. Alpha quartz is generally found in nature. When quartz is heated above 1,063.4°F (573°C), it turns into beta quartz. Manufacturing processes create this change, but lightning or meteors can also complete the process.
A component of soil and sand, crystalline silica is often used in the production of glass. When heated, the SiO2-containing sand hardens into the glass. The first recorded glass production was in Egypt about 5,000 years ago.
In addition to sand, crystalline silica is found in all kinds of rock formations. Igneous rocks have the least amount of quartz when compared to sedimentary or metamorphic rocks. Igneous rock, made up of lava, contains silicon, oxygen, and metals, so silicon is usually formed. If an excess of silicon and oxygen remains after the metal is depleted, quartz will also form. About 12% of igneous rocks are SiO2.
Crystalline silica is used in many manufacturing industries, as well as in ceramics, glass manufacturing, and for plastic and rubber fillers. Also, it is found in concrete, granite, sandstone and other types of stones. Many famous structures, such as the White House in Washington, DC, contain crystalline silica.
Working with crystalline silica can be dangerous. The dust generated by drilling or cutting quartz is easily inhaled and causes silicosis, which creates scar tissue in the lungs and makes an affected person more susceptible to other lung diseases, such as tuberculosis. Use extreme caution when working with this material.
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