Home Science Dictionaries thesauruses pictures and press releases amphiboles

amphiboles

A Dictionary of Earth Sciences
© A Dictionary of Earth Sciences 1999, originally published by Oxford University Press 1999.

amphiboles A group of minerals possessing double chains of silicon—oxygen [SiO4] tetrahedra with a composition of [Si4O11]n running parallel to the crystallographic axis; i.e. parallel to the prism zone of a crystal. The double chains are held together by monovalent, divalent, or trivalent cations, of which Na+, Ca2+, Mg2+, Fe2+, Al3+, and Fe3+ are the most important; hydroxyl ions also occur. There are three main groups of amphibole minerals: (a) calcium-poor amphiboles with the general formula X2Y5[Z4O11]2(OH,F)2, where X = Mg or Fe2+, Y = Mg, Fe2+, Fe3+, Al3+, etc., and Z = Si or Al; (b) the calcium-rich amphiboles with the general formula AX2Y5[Z4O11]2(OH,F)2, where A = Na, X = Ca, Y = Mg, Fe2+, Fe3+, Al, etc., and Z = Si or Al; and (c) the alkali amphiboles in which Na > Ca and with the general formula AX2Y5[Z4O11]2(OH,F)2, where A = Na or K, X = Na (or Na and Ca), Y = Mg, Fe2+, Fe3+, Al, etc., and Z = Si or Al. Calcium-poor amphiboles include the orthorhombic amphiboles (called the orthoamphiboles) and include anthophyllite and gedrite, but the other two groups are monoclinic and include the common hornblendes tremolite and actinolite, as well as the sodium-rich varieties such as glaucophane and riebeckite. Amphiboles are common rock-forming silicate minerals that occur in intermediate and alkaline igneous rocks and also in many regional metamorphic rock types.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"amphiboles." A Dictionary of Earth Sciences. . Encyclopedia.com. 21 Jan. 2019 <https://www.encyclopedia.com>.

"amphiboles." A Dictionary of Earth Sciences. . Encyclopedia.com. (January 21, 2019). https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/amphiboles

"amphiboles." A Dictionary of Earth Sciences. . Retrieved January 21, 2019 from Encyclopedia.com: https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/amphiboles

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.