silica

sil·i·ca   (sĭl'ĭ-kə)    n.  A white or colorless crystalline compound, SiO2, occurring abundantly as quartz, sand, flint, agate, and many other minerals and used to manufacture a wide variety of materials, especially glass and concrete. [New Latin, from Latin silex, silic-, hard stone, flint.]

silica 

Main Entry: sil·i·ca
Pronunciation: 'sil-i-k&
Function: noun
: the dioxide of silicon SiO₂ that is used as an ingredient ofsimethicone and that occurs naturally in crystalline, amorphous, and impure forms (as in quartz, opal, and sand respectively) called also silicon dioxide

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.

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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