How Do You Rate This Publication?       

Title:	Clay Minerals
Author(s):	Barton, C.D.
Date:	2002
Source:	In: Rattan Lal, comp., ed. Encyclopedia of Soil Science. New York, New York: Marcel Dekker: 187-192.
Description:	Clay minerals refers to a group of hydrous aluminosilicates that predominate the clay-sized (<2 m) fraction of soils. These minerals are similar in chemical and structural composition to the primary minerals that originate from the Earth's crust; however, transformations in the geometric arrangement of atoms and ions within their structures occur due to weathering. Primary minerals form at elevated temperatures and pressures, and are usually derived from igneous or metamorphic rocks. Inside the Earth these minerals are relatively stable, but transformations may occur once exposed to the ambient conditions of the Earth's surface. Although some of the most resistant primary minerals (quartz, micas, and some feldspars) may persist in soils, other less resistant minerals (pyroxenes, amphiboles, and a host of accessory minerals) are prone to breakdown and weathering, thus forming secondary minerals. The resultant secondary minerals are the culmination of either alteration of the primary mineral structure (incongruent reaction) or neoformation through precipitation or recrystallization of dissolved constituents into a more stable structure (congruent reaction). These secondary minerals are often referred to as phyllosilicates because, as the name implies (Greek: phyllon, leaf), they exhibit a platy or flaky habit, while one of their fundamental structural units is an extended sheet of SiO tetrahedra.
	View and Print this Publication (73 KB)
Pristine Version:	An uncaptured or "pristine" version of this publication is available. It has not been subjected to OCR (Optical Character Recognition) and therefore does not have any errors in the text. However it is a larger file size and some people may experience long download times. The "pristine" version of this publication is available here: View and Print the PRISTINE copy of this Publication (749 KB)
Publication Notes:	We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information. This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain. Our on-line publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS Webmaster, srswebmaster@fs.fed.us if you notice any errors which make this publication unuseable.
	Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility