(1) For some animals, developing hard shells of silica , or incorporating calcium in bones and teeth, has clear benefits.

(2) The silicate minerals are those that contain silica , a combination of silicon and oxygen.

(3) The silica and other minerals in the clay vitrify under heat and will not become soft clay again.

(4) Soluble silicates can be obtained by heating alkali metal carbonates and silica .

(5) Chert is a finely crystalline silica that commonly forms in association with hot springs.

(6) Quartz and sand are composed of silicon and oxygen alone: silicon dioxide, or silica .

(7) Several powders or dry colours use a base of asbestos, chalk powder or silica .

(8) Sandy soil attached to the furs was the source of silica in the fur dust.

(9) In the fossilisation process, the original organic parts of the shark's tooth are replaced by minerals such as iron pyrites and silica .

(10) The host limestone surrounding the pockets has been largely replaced by silica and iron oxides.

(11) Soils are generally clay silica of varied depths and exposures.

(12) Cristobalite is a crystalline form of silica that has a diamondlike structure.

(13) Precipitation of gold is favoured by similar conditions to those that favour precipitation of silica .

(14) Glass is made from silica the most common mineral on the planet and aluminium is the most abundant metal on earth.

(15) When serpentine dissolves in sulfuric acid, the silicon in the mineral becomes silicon dioxide , or sand, and falls to the bottom, while the magnesium becomes magnesium sulfate.

(16) Precious metals are commonly precipitated with the siliceous sinters that form around hot springs and geysers.

(17) The most common minerals are those that contain silicon dioxide in one form or another.

(18) Tectonic ironstone encompasses siliceous and ferruginous rock types that are characterized by the presence of chert or cherty quartzite, iron sulphides and their alteration products.

(19) Early in the 1800s, mineralogists recognized that tiger's-eye was a fibrous variety of quartz, or silicon dioxide .

(20) Quartz is the dominant mineral in veins in siliceous rocks, calcite in limestones, and gypsum in gypsiferous sediments.