agate


agate
agatelike, agatoid, adj.
/ag"it/, n.
1. a variegated chalcedony showing curved, colored bands or other markings.
2. a playing marble made of this substance, or of glass in imitation of it.
3. Print. a 51/2-point type of a size between pearl and nonpareil. Cf. ruby (def. 5).
[1150-1200; ME ac(c)ate, achate, agaten (cf. D agaat, OS agat, OHG agat), appar. < OF agathe or It agata (initial stress) ML achates < Gk achátes]

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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.

Banded agate

B.M. Shaub

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 common semiprecious silica mineral, a variety of chalcedony (q.v.) that occurs in bands of varying colour and transparency. Agate is essentially quartz, and its physical properties are in general those of that mineral. See silica mineral (table).

      Agate is found throughout the world. In the United States it is produced in several western states; Oregon, Washington, Idaho, and Montana are the chief sources of gemstones. Most agates occur in cavities in eruptive rocks or ancient lavas. These agates have a banded structure, successive layers being approximately parallel to the sides of the cavity. It is probable that they have been formed as follows. During cooling of the lava, steam and other gases form bubbles. The bubbles overtaken by solidification are frozen in, forming cavities. Long after the rock has solidified, water—carrying silica (q.v.) in solution, probably as alkali silicate—penetrates into the bubble and coagulates to a silica gel. Soluble components of the iron-bearing rock diffuse into the silica gel and produce the regular layers of iron hydroxide. Finally the whole mass gradually hardens with loss of water and crystallization of much of the silica as quartz or chert. During crystallization, the coloured bands are not disturbed. Varieties of agate are characterized by peculiarities in the shape and colour of the bands, which are seen in sections cut at right angles to the layers. In riband agate the bands appear as straight lines in cross section. Such agate, with white bands alternating with bands of black, brown, or red, is called onyx (q.v.). A ring or eye agate has concentric circular bands of different colours. A variety having included matter of a green colour, embedded in the agate and disposed in filaments and other forms suggestive of vegetable growth, is known as moss agate (q.v.).

      The agate-working industry grew up centuries ago in the Idar-Oberstein district of Germany, where agates were abundant. After 1900 most agates were supplied by Brazil and Uruguay. Most commercial agate is artificially stained so that stones unattractive because of their dull-gray tints become valuable for ornamental purposes.

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Universalium. 2010.

Look at other dictionaries:

  • agate — agate …   Dictionnaire des rimes

  • agate — [ agat ] n. f. • XIIIe; acate XIIe; lat. achates, gr. akhatês 1 ♦ Minér. Variété de calcédoine, finement zonée, aux teintes nuancées et contrastées, utilisée comme pierre précieuse (camées, coupes, etc.). ♢ Objet d art en agate. Les agates… …   Encyclopédie Universelle

  • agate — AGATE. s. f. Pierre de la nature du caillou; elle est fort dure et prend parfaitement le poli; elle donne des étincelles lorsqu on la frappe avec de l acier, et elle varie pour les couleurs, les veines et les accidens qui s y trouvent. Les agates …   Dictionnaire de l'Académie Française 1798

  • Agate — Ag ate, n. [F. agate, It. agata, L. achates, fr. Gr. ?.] 1. (Min.) A semipellucid, uncrystallized variety of quartz, presenting various tints in the same specimen. Its colors are delicately arranged in stripes or bands, or blended in clouds.… …   The Collaborative International Dictionary of English

  • agaté — agaté, tée (a ga té, tée) adj. Qui contient de l agate. Jaspe agaté. ÉTYMOLOGIE    Agate …   Dictionnaire de la Langue Française d'Émile Littré

  • agate — AGÁTE s.f.pl. Litere tipografice a căror floare corespunde unei litere de şase puncte. [sg. agată. / cf. fr. agate]. Trimis de LauraGellner, 13.09.2007. Sursa: DN  AGÁTE s. f. pl. litere tipografice cu floarea de şase puncte. (< fr. agate) …   Dicționar Român

  • agate — [ag′it] n. [ME agaten < OFr agate < ML < L achates < Gr achatēs < ?] 1. a hard semiprecious stone, a variety of chalcedony, with striped or clouded coloring 2. any of various tools having agate parts, as a burnishing instrument… …   English World dictionary

  • Agate — A*gate , adv. [Pref. a on + gate way.] On the way; agoing; as, to be agate; to set the bells agate. [Obs.] Cotgrave. [1913 Webster] …   The Collaborative International Dictionary of English

  • agate — (n.) 1560s, from M.Fr. agathe (16c.), from L. achates, from Gk. akhates, the name of a river in Sicily where the stones were found (Pliny). But the river could as easily be named for the stone. The earlier English form of the word, achate (early… …   Etymology dictionary

  • agate — AGATE. s. f. Sorte de pierre precieuse qui n est point transparente. Agate d Orient. agate de Boheme …   Dictionnaire de l'Académie française

  • agate —    , agate line    a traditional unit of area used in printing and advertising. The agate line is equal to 1/14 inch (1.814 millimeters) multiplied by the width of the printed line. Its name comes from the traditional type size called agate,… …   Dictionary of units of measurement


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