GC: n
CT: Silica is the name given to a group of minerals composed of silicon and oxygen, the two most abundant elements in the earth’s crust. Silica is found commonly in the crystalline state and rarely in an amorphous state. It is composed of one atom of silicon and two atoms of oxygen resulting in the chemical formula SiO2.
The first industrial uses of crystalline silica were probably related to metallurgical and glass making activities in three to five thousand years BC. It has continued to support human progress throughout history, being a key raw material in the industrial development of the world especially in the glass, foundry and ceramics industries. Silica contributes to today’s information technology revolution being used in the plastics of computer mouses and providing the raw material for silicon chips.
S: http://www.eurosil.eu/what-silica (last access: 12 July 2016)
N: 1. “hard silicon dioxide,” 1801, Modern Latin, from Latin silex (genitive silicis) “flint, pebble,” on model of alumina, soda.
2. 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.
3. Silica is another name for the chemical compound silicon dioxide. Each unit of silica includes one atom of silicon and two atoms of oxygen.
4. Silica exists in nine different crystalline forms or polymorphs with the three main forms being quartz, which is by far the most common, tridymite and cristobalite. It also occurs in a number of cryptocrystalline forms. Fibrous forms have the general name chalcedony and include semi-precious stone versions such as agate, onyx and carnelian. Granular varieties include jasper and flint. There are also anhydrous forms – diatomite and opal.
Quartz is the second most common mineral in the earth’s crust. It is found in all three of the earths rock types – igneous, metamorphic and sedimentary. It is particularly prevalent in sedimentary rocks since it is extremely resistant to physical and chemical breakdown by the weathering process. Since it is so abundant, quartz is present in nearly all mining operations. It is present in the host rock, in the ore being mined, as well as in the soil and surface materials above the bedrock, which are called the overburden.
5. People get confused about the differences between silicon, silicate, silica and even silicone.
- Silicon: It is a chemical element, one of the 97 natural building blocks from which our minerals are formed.
- Silica and silicate: Silica is a bit trickier concept. It refers the combination of silicon plus oxygen. The mineral quartz is silica. But so are the minerals tridymite, coesite, cristobalite and stishovite which are mineral forms of silica that are stable at high temperatures and pressures. All these minerals are also silicates. In other words, quartz is a silicate made of pure silica. But feldspars contain sodium, aluminum, potassium and calcium in addition to silicon and oxygen. Thus feldspars are silicates but they aren’t pure silica. Silicon links up with oxygen (which makes up 55% of the earth’s crust) to form the most common suite of minerals, called the silicates. Quartz, feldspars, olivine, micas, thomsonite, jadeite, and prehnite are all silicates. There is so much oxygen around that pure native silicon is almost never found naturally.
- Silicone: Its a synthetic polymer of silicon with carbon and oxygen that could be in solid, liquid or gel form. It has all kinds of medical uses, such as in antacids, artificial joints, pacemakers and implants of various notoriety, but is not, as far as anyone knows, found in rocks.
S: 1. OED – http://www.etymonline.com/index.php?term=silica (last access: 12 July 2016). 2 & 3. http://study.com/academy/lesson/what-is-silica-properties-definition-quiz.html (last access: 12 July 2016). 4. http://www.eurosil.eu/what-silica (last access: 12 July 2016). 5. https://minds.wisconsin.edu/bitstream/1793/11591/1/Silicon.pdf (last access: 12 July 2016).
SYN: silicon dioxide, SiO2, silicic anhydride.
S: GDT – http://www.granddictionnaire.com/ficheOqlf.aspx?Id_Fiche=8367047 (last access: 12 July 2016)
