The lightweight porous opaline variety of silica, white or nearly white,
deposited as an incrustation by precipitation from the waters of geysers
and hot springs. The term has been applied loosely to any deposit made by
a geyser or hot spring. Syn:sinter; pearl sinter; geyserite; fiorite.
AGI
a. In petrology, containing silica in dominant amount.
b. In chemistry, containing silicon as the acid-forming element.
c. Said of a silica-rich igneous rock or magma. Although there is no firm
agreement among petrologists, the amount of silica is usually said to
constitute at least 65% or two-thirds of the rock. In addition to the
combined silica in feldspars, silicic rocks generally contain free silica
in the form of quartz. Granite and rhyolite are typical silicic rocks. The
synonymous terms "acid" and "acidic" are used almost as frequently as
silicic. Syn:acidic; intermediate; persilicic. CF:basic; ultrabasic.
AGI
a. The introduction of, or replacement by, silica, generally resulting in
the formation of fine-grained quartz, chalcedony, or opal, which may fill
pores and replace existing minerals. CF:silication
Syn:silification
b. A process of fossilization whereby the original organic components of
an organism are replaced by silica, as quartz, chalcedony, or opal.
AGI
Adj. of silicification.
A material formed by replacement of wood by silica in such manner that the
original form and structure of the wood is preserved. The silica is
generally in the form of opal or chalcedony. Syn:petrified wood;
woodstone; agatized wood; fossilized wood; opalized wood; shinarump.
Said of the silica cement of a sedimentary rock. AGI
See:natural ore
A nonmetallic element that is the second most abundant on Earth, being
exceeded only by oxygen. Symbol, Si. Silicon is not found free in nature,
but occurs as the oxide and silicate. Sand, quartz, rock crystal,
amethyst, agate, flint, jasper, and opal are some of the forms in which
the oxide appears. Hornblende, orthoclase, kaolin, and biotite are a few
of the numerous silicate minerals. Used in the electronics and space-age
industries; used to make concrete, brick, and glass. Miners often develop
a serious lung disease, silicosis, from breathing large quantities of the
dust. Handbook of Chemistry and Physics, 3
Silicon bronze is a noncorroding alloy with copper and tin. Silicon copper
(70% to 80% copper and 20% to 30% silicon) is an alloy added to molten
copper or brass to remove oxygen. Silicon iron is a grain-improved iron,
corrosion resistant. See also:ferrosilicon
Two compounds have been reported: SiB4 , oxidation resistant to
1,370 degrees C; SiB6 , melting point 1,950 degrees C. A special
refractory has been made by reacting silicon and boron in air, the product
containing SiB4 and Si in a borosilicate matrix; it is stable in
air to at least 1,550 degrees C and has good thermal shock resistance.
Syn:boron silicides
A rich copper alloy added to molten copper in order to secure clean, solid
castings free from blowholes, swellings, etc. Crispin
See:silica
To unite or cause to unite with silicon, as in the combination of iron
with silicon in certain metallurgical processes. Standard, 2
A fundamental structural unit of silicate minerals formed by four oxygen
ions surrounding one silicon ion such that lines connecting the four
oxygen nuclei show the outline of a geometric tetrahedron. It is commonly
written SiO4 with the electronic charge of minus 4 for the unit
assumed. See also:silicate
a. A spiegeleisen containing 15% to 20% manganese and 8% to 15% silicon
used in making certain special steels. Webster 3rd
b. A form of pig iron. Henderson
A variety of steel containing up to 5% silicon. It is very hard, but is
brittle and difficult to work.
a. Lung disease caused chiefly by inhaling rock dust from air drills.
Nichols, 1
b. A condition of massive fibrosis of the lungs marked by shortness of
breath and resulting from prolonged inhalation of silica dusts by
those--such as stonecutters, asbestos workers, miners--regularly exposed
to such dusts. See also:pneumoconiosis; simple silicosis;
mining disease. Webster 3rd
Complication of tuberculosis by silica. Hartman, 1
See:silicification
Microscopically small, needlelike inclusions of rutile crystals in a
natural gem, such as ruby, sapphire, or garnet, from which subsurface
reflections produce a whitish sheen resembling that of silk fabric.
A finely ground-plastic clay of high refractoriness used as a bond for
molding sands. Osborne