These ores always contain impurities, such as silica, sulphides, and earthy materials.
It is composed of silica, alumina, carbonate of lime, magnesia and oxide of iron.
It is not unlike flint, and flint is one of the mineral forms of silica.
Many of these knives have silica blades, some of the handles being of jade.
In the formation of slag from these materials the ore is freed from the silica and aluminium which it contained.
The residuum may be examined for silica, lime, barytes, and oxide of titanium.
silica was almost certainly an oxide; but electro-negative oxides are, as a class, acids; therefore silica was probably an acid.
It consists of silica 25; protoxide of manganese 60; water 13.
For instance, shells originally composed of carbonate of lime are often found to have been turned into flint or silica.
Acid lavas are those in which the quantity of silica is greatest.
"hard silicon dioxide," 1801, Modern Latin, from Latin silex (genitive silicis) "flint, pebble," on model of alumina, soda.
silica sil·i·ca (sĭl'ĭ-kə)
A crystalline compound occurring abundantly as quartz, sand, and many other minerals and used to manufacture a variety of materials, especially glass and concrete.
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.