Gallium oxide is less volatile than silica ( the main constituent of tektites ) and germanium oxide is more volatile.

Libyan Desert silica-glass, another natural glass, is composed of nearly pure silica and has the same trace germanium content as sands in the area.

Agate () is a microcrystalline variety of silica, chiefly chalcedony, characterised by its fineness of grain and brightness of color.

In the formation of an ordinary agate, it is probable that waters containing silica in solution — derived, perhaps, from the decomposition of some of the silicates in the lava itself — percolated through the rock and deposited a siliceous coating on the interior of the vapour-vesicles.

One proposed reaction is that of the olivine-rich rock dunite, or its hydrated equivalent serpentinite with carbon dioxide to form the carbonate mineral magnesite, plus silica and iron oxide ( magnetite ).

If matrix support is polar ( e. g. paper, silica etc.

Methods in which the stationary phase is more polar than the mobile phase ( e. g., toluene as the mobile phase, silica as the stationary phase ) are termed normal phase liquid chromatography ( NPLC ) and the opposite ( e. g., water-methanol mixture as the mobile phase and C18 = octadecylsilyl as the stationary phase ) is termed reversed phase liquid chromatography ( RPLC ).

However, silica fume is more usually added to Portland cement at the concrete mixer.

If the magma is rich in silica, the caldera is often filled in with ignimbrite, tuff, rhyolite, and other igneous rocks.

The magma feeding these volcanoes is basalt which is silica poor.

For example, dynamite is a mixture of highly sensitive nitroglycerin with sawdust, powdered silica, or most commonly diatomaceous earth, which act as stabilizers.

For example, silica is functionalized with an alkyl silicone, wherein the alkyl contains an amine functional group.

These are often incompressible diatomaceous earth, or kieselguhr, which is composed primarily of silica.

The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75 % silica ( SiO < sub > 2 </ sub >) plus sodium oxide Na < sub > 2 </ sub > O from soda ash, lime CaO, and several minor additives.

Sand | Quartz sand ( silica ) is the main raw material in commercial glass production

The resulting glass contains about 70 to 74 % silica by weight and is called a soda-lime glass.

All silicate minerals have a base unit of a < sup > 4 -</ sup > silica tetrahedra — that is, a silicon cation coordinated by four oxygen anions, which gives the shape of a tetrahedron.

Cleavage is not a universal property among minerals ; for example, quartz, consisting of extensively interconnected silica tetrahedra, does not have a crystallographic weakness which would allow it to cleavage, whereas micas — which have perfect basal cleavage — consist of sheets of silica tetrahedra which are very weakly held together.

The silica polymorph that is most stable at the Earth's surface is α-quartz.

Covalently bonded crystals are also very common, notable examples being diamond, silica, and graphite.

Although most free silicon is used in the steel refining, aluminum-casting, and fine chemical industries ( often to make fumed silica ), the relatively small portion of very highly purified silicon that is used in semiconductor electronics (< 10 %) is perhaps even more critical.

This magma tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth.

At very high pressure, even SiO < sub > 2 </ sub > adopts this geometry in the mineral stishovite, a dense polymorph of silica found in the lower mantle of the Earth.

They have very low percentages of silica but much iron and magnesia.

The net result is a very broad spectrum ( 30 nm in silica, typically ).

At very low degrees of partial melting a silica undersaturated melt is produced, forming a nepheline syenite, where orthoclase is replaced by a feldspathoid such as leucite, nepheline or analcime.

Chalcedony () is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite.

" Ultramarine rich in silica " is generally obtained by heating a mixture of pure clay, very fine white sand, sulfur and charcoal in a muffle-furnace.

We do know that in a very short course of time just before the Cambrian period exoskeletons made of various materials – silica, calcium phosphate, calcite, aragonite, and even glued-together mineral flakes – sprang up in a range of different environments.

Although pure silica is a perfectly viable glass and glass fiber, it must be worked with at very high temperatures, which is a drawback unless its specific chemical properties are needed.

Most traditional HPLC is performed with the stationary phase attached to the outside of small spherical silica particles ( very small beads ).

For instance, reagent-quality water must have very low levels of impurities like sodium and chloride ions, silica, and bacteria, as well as a very high electrical resistivity.

The high density and hardness (~ 5 on the Mohs Hardness Scale ) together with a high degree of angularity, make some types of volcanic ash ( particularly those with a high silica content ) very abrasive.

Because of poisonous dopants ( see below ) and their very high absorption of moisture, silica gel packets usually bear warnings for the user not to eat the contents.

Molten silica is a very good solvent for metal oxides and scavenges small particles easily ; explosions above silica-containing soils will produce particles with isotopes mixed through their volume.

Their strong affinity for oxygen causes lithophile elements to associate very strongly with silica, forming relatively low-density minerals that thus float to the crust.

Basalt is a very common volcanic rock with low silica content.

Inhaled silica can cause silicosis and ( in very rare cases ) can encourage the development of cancer.

SHARP materials are very robust and would not require constant maintenance, as is the case with technologies like silica tiles, used on the Space Shuttle, which account for over half of that vehicles maintenance costs and turnaround time.

Pneumonoultramicroscopicsilicovolcanoconiosis is, according to the Oxford English Dictionary, " a factitious word alleged to mean ' a lung disease caused by the inhalation of very fine silica dust, causing inflammation in the lungs.

* Transparent silica aerogel would be very suitable as a thermal insulation material for windows, significantly limiting thermal losses of buildings.