silica

[sil-i-kuh]
noun
the dioxide form of silicon, SiO 2 , occurring especially as quartz sand, flint, and agate: used usually in the form of its prepared white powder chiefly in the manufacture of glass, water glass, ceramics, and abrasives.
Also called silicon dioxide.


Origin:
1795–1805; < Neo-Latin, derivative of Latin silex silex

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World English Dictionary
silica (ˈsɪlɪkə)
 
n
1.  the dioxide of silicon, occurring naturally as quartz, cristobalite, and tridymite. It is a refractory insoluble material used in the manufacture of glass, ceramics, and abrasives
2.  short for silica glass
 
[C19: New Latin, from Latin: silex]

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Etymonline
Word Origin & History

silica
"hard silicon dioxide," 1801, Mod.L., from L. silex (gen. silicis) "flint, pebble."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

silica sil·i·ca (sĭl'ĭ-kə)
n.
A crystalline compound occurring abundantly as quartz, sand, and many other minerals and used to manufacture a variety of materials, especially glass and concrete.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
silica   (sĭl'ĭ-kə)  Pronunciation Key 
A chemical compound that is the main constituent of most of the Earth's rocks. Silica occurs naturally in five crystalline forms (quartz, tridymite, cristobalite, coesite, and stishovite), in a cryptocrystalline form (chalcedony), and in an amorphous form (opal). It is also the main chemical compound in sand. Silica is used to make glass, concrete, and other materials. Also called silicon dioxide. Chemical formula: SiO2.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

silica

compound of the two most abundant elements in the Earth's crust, silicon and oxygen, SiO2. The mass of the 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.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Under a high-powered microscope the silica shells of single-celled algae are
  revealed in all their manifold beauty.
Lighter materials, such as the mineral silica, rose to the surface.
Raw materials, including silica and plant ash, were heated inside ovoid vessels
  that might have been recycled beer jars.
Similar reflective structures made from silica are also responsible for the
  shimmering color found in opals.
Image for silica
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