agate (ăg`ĭt), translucent, cryptocrystalline variety of quartz quartz, one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO₂.
..... Click the link for more information. and a subvariety of chalcedony chalcedony [from Chalcedon], form of quartz the crystals of which are so minute that its crystalline structure cannot be seen except with the aid of a microscope. Chalcedony has a waxy luster and is translucent to transparent.
..... Click the link for more information. . Agates are identical in chemical structure to jasper, flint, chert, petrified wood, and tiger's-eye, and are often found in association with opal. The colorful, banded rocks are used as a semiprecious gemstone and in the manufacture of grinding equipment. An agate's banding forms as silica from solution is slowly deposited into cavities and veins in older rock. The stones can be artificially stained to produce combinations of color more vivid than those found in the natural state. The cutting and staining of agates has long been centered at Idar-Oberstein, Germany. Important sources of agate are Brazil, Uruguay, and the United States (Oregon, Washington, and around Lake Superior). The moss agate or mocha stone contains visible impurities in the form of dendritic shapes that resemble moss. See onyx onyx , variety of cryptocrystalline quartz, differing from agate only in that the bands of which it is composed are parallel and regular. Its appearance is most striking when the bands are of sharply contrasting colors; black and white specimens are often used for
..... Click the link for more information. .

agate

Banded agate

(credit: B.M. Shaub)

Common, semiprecious silica mineral, a variety of chalcedony that occurs in bands of varying colour and transparency. Varieties are characterized by peculiarities in the shape and colour of the bands, which are seen in sections cut at right angles to the layers. Agate is found throughout the world, commonly in cavities in eruptive rocks and in geodes. Brazil and Uruguay are major producers of agates; they are also found in Oregon, Washington, Idaho, Montana, and other western U.S. states. Agate is essentially quartz. Much commercial agate is artificially dyed to make the naturally dull-gray stones more colourful.

agate

1. an impure microcrystalline form of quartz consisting of a variegated, usually banded chalcedony, used as a gemstone and in making pestles and mortars, burnishers, and polishers. Formula: SiO₂

2. a playing marble of this quartz or resembling it

agate [′ag·ət]

(graphic arts)

A type size in printing of about 5½ points, where 72 points equals 1 inch.

(mineralogy)

SiO₂A fine-grained, fibrous variety of chalcedony with color banding or irregular clouding.

agate

symbolizes health; supposed to relieve snake and scorpion bites. [Class. and Medieval Legend: Leach, 27]

See : Health

agate

confers this power. [Rom. Folklore: Brewer Dictionary,15]

See : Invisibility

a mineral; a variety of chalcedony in the form of a dense, cryptocrystalline aggregate of fibrous or radial quartz formations (Si0₂)—so-called quartzite or α-tridymite. The mineral is characterized by multiple interstratification of thin (up to 10 microns), variously colored layers. The hardness of agate on the mineralogical scale is 6.0–6.5. The following varieties are recognized depending on the combination of colors in the layers—onyx (white and black layers), carnelian (red and white), sardonyx (reddish brown and white), and agates (bluish gray and white). Agate occurs in veins, in geodes, in amygdules among igneous rocks, and in the tuffs of the last. It is used as an industrial or semiprecious stone and in the manufacture of technical articles (bearing stones, prisms for scales, and so on). Agate is colored artificially to obtain bright, decorative forms.

G. P. BARSANOV

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Agate (redirected from Greek agate)

agate

Agate
(redirected from Greek agate)