Euhedral

Euhedral

Euhedral crystals are those that are well-formed with sharp, easily-recognized faces. Normally, crystals do not form smooth faces or sharp crystal outlines. Many crystals grow from cooling liquid magma. As magma cools, the crystals grow and eventually touch each other, preventing crystal faces from forming properly or at all.

However, when snowflakes crystallize, they do not touch each other. Thus, snowflakes form euhedral, six-sided twinned crystals. In rocks, the presence of euhedral crystals may signify that they formed early in the crystallization of a magma or perhaps crystallized in a cavity or vug, without hindrance from other crystals.

By contrast, a rock with an "anhedral texture" is composed of mineral grains that have no well formed crystal faces or cross-section shape in thin section. Anhedral crystal growth occurs in a competitive environment with no "free space" for the formation of crystal faces. An intermediate texture with some crystal face formation is termed "subhedral".

Etymology: Euhedral is derived from the Greek "hedron" meaning "shape".

References

* Hurlbut, Cornelius S.; Klein, Cornelis, 1985, "Manual of Mineralogy," 20th ed., Wiley, p. 15 ISBN 0-471-80580-7


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • euhedral — /yooh hee dreuhl/, adj. Petrog. idiomorphic (def. 1). [1905 10; EU + HEDRAL] * * * …   Universalium

  • euhedral — adjective Having sharp, recognisable crystal faces …   Wiktionary

  • euhedral — eu|he|dral <Adj.> [zu griech. eũ = gut, wohl u. hédra = Sitz; Grundlage]: idiomorph …   Universal-Lexikon

  • euhedral — eu|he|dral* <zu gr. eúhedros »gut, fest sitzend« u. 1↑...al> svw. ↑idiomorph …   Das große Fremdwörterbuch

  • euhedral — [ju: hi:dr(ə)l] adjective Geology (of a mineral crystal) having faces corresponding to its regular crystal form, not constrained by adjacent minerals …   English new terms dictionary

  • euhedral — eu·he·dral …   English syllables

  • euhedral — (ˈ)yü|hēdrəl adjective Etymology: eu + hedral : idiomorphic …   Useful english dictionary

  • igneous rock — Any of various crystalline or glassy, noncrystalline rocks formed by the cooling and solidification of molten earth material (magma). Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary …   Universalium

  • Rock microstructure — includes the texture of a rock and the small scale rock structures. The words texture and microstructure are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable because it is a useful… …   Wikipedia

  • Lamprophyre — Lamprophyres (Greek λαµπρός (lamprós) = bright and φύρω (phýro) = to mix) are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions. They are alkaline silica… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”