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Laterite vs. clay

Date: Sun, 24 Jan 1999 08:22:05 -0500
From: krandall at world_std.com
Subject: Laterite vs. clay

Karen wrote:
> Huh?  It has always been my impression that laterite _is_ clay.  Just a
> very specific type of clay.

Correct. Clay, by definition, is soil of particle size 5 micrometers and
less (or agglomerates thereof).

> Do you have any documentation to support the supposition that it is not
> clay?  It certainly _acts_ like clay... You can dry it, wet it, mold it...

Clays differ mostly by the formation method. Due to fast leeching, many
temperate zone clays have a high silicate component (usually hydrated),
where tropical clays may have been further slow-leeched to the *oxides*
of aluminum, iron, etc. This is why temperate clays often have high CEC
and tropical clays don't.

Laterite and other tropical clays don't swell much, either, when wetted.
Montmorillonite (kitty litter), bentonite, and many temperate zone clays
swell a great deal, opening surface area to assist in cation exchange.

They differ profoundly, both pysically and chemically. IDK what that
means, though, when we use them as part of our substrate mix.


Wright Huntley, Fremont CA, USA, 510 494-8679  huntley1 at home dot com

Liberalism is totalitarianism with a human face.
                                  Thomas Sowell