silica

The amorphous structure of glassy silica in two-dimensions. No long-range order is present; however there is local ordering with respect to the tetrahedral arrangement of oxygen (O) atoms around the silicon (Si) atoms. Note that a fourth oxygen atom is bonded to each silicon atom, either behind the plane of the screen or in front of it; these atoms are omitted for clarity. Source: Wikipedia

A white or colorless mineral composed of silicon dioxide (SiO₂). It occurs commonly as quartz and sand, and in many other familiar rocks and minerals, including flint, granite, amethyst, and rock-crystal. Silica is refractory and inert, though it dissolves in hydrogen fluoride and reacts with bases to form silicates. It is used to make glass, ceramics, concrete, and carborundum.

Silica gel

Silica gel is an amorphous form of silica made by acidifying a silicate and dehydrating the silicic acid formed. It is widely used as an adsorbent (see adsorption and drying agent. See also gel.

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• GEOLOGY AND PLANETARY SCIENCE

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