What is Silica? - Properties & Definition

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  • 0:01 Silica Defined
  • 0:50 Properties of Silica
  • 2:09 Facts About Silica
  • 3:38 Lesson Summary
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Lesson Transcript
Instructor: Mary Ellen Ellis
Silica is the most abundant mineral in the earth's crust, but you might not know much about it. Quartz, sand, and glass are all made of silica. Learn more about the properties and uses of this plentiful mineral.

Silica Defined

Silica is another name for the chemical compound silicon dioxide. Each unit of silica includes one atom of silicon and two atoms of oxygen.

If you have never heard of silica before, you might be surprised to hear that you probably come into contact with it every day. Silica makes up the mineral called quartz, and it is the most abundant mineral in the earth's crust. It is the main component of most sand and the primary ingredient in glass. Every time you pick up a glass to take a drink, you are using silica.

Silica has been known to humans since ancient times, long before we knew it was made of silicon and oxygen. The art of making glass objects with silica dates back centuries. Today, there are many industrial uses for silica. These include abrasives, building materials, fillers, electronics, and water filtration.

Properties of Silica

The properties of silica include both chemical and physical properties such as hardness, color, melting and boiling point, and reactivity. Silica under normal conditions of temperature and pressure is a solid, crystallized mineral. It is relatively hard, rating a 7 on the Mohs scale, a scale used to measure the hardness of minerals relative to each other. The hardest mineral, diamond, rates 10 on the scale.

Pure silica is colorless, but if contaminants are present in a sample of quartz, it may be colored. For instance, rose quartz is silica with trace amounts of iron. This gives it a pinkish hue. Milky quartz is simply silica with air bubbles or inclusions of liquid that make the mineral appear white.

Silica has very high melting and boiling points: 3,110 °F and 4,046 °F. It takes a big, hot furnace to melt silica sand in order to make glass! Silica reacts with hydrofluoric acid. This reaction is used to etch quartz in the semiconductor industry. Silica also reacts with metal oxides like sodium oxide or lead oxide. These reactions are used to produce different types of glass, such as borosilicate glass or leaded glass. Borosilicate glass is a type of glass that can handle temperature extremes. It is often used in glassware for laboratories.

Facts About Silica

Silica is a diverse and interesting mineral. It's found abundantly throughout the earth, and, in fact, oxygen and silicon are the number one and two, respectively, most abundant elements in the earth's crust.

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