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Laterite and Aluminum Silicate

---------- Forwarded message ----------
From: Stephen.Pushak at saudan_HAC.COM
Subject: Laterite & Aluminum Silicate
To: Aquatic-Plants at actwin_com
Date: Tue, 11 Mar 1997 18:29:03 PST
Cc: psears at nrn1_NRCan.gc.ca, jpp at inforamp_net

First let me get my question out of the way; this is to the chemists:

Aluminum silicates (of various forms) are one of the most common 
structures found in natural soils. There seems to be some uncertainty
over whether tropical, volcanic laterite (of the type mined by Dupla)
actually contains aluminum or more specifically aluminum silicates.
(I suppose it's only uncertain to me, not to geologists ;-)

1) How probable is it that aluminum silicates could be leached from
soils under tropical conditions (i.e. mildly acidic water in large

2) How reactive are aluminum silicates in clay form in the substrate
under low redox conditions and with possibly low pH (~6 pH) ? 

> From: "James Purchase" <jpp at inforamp_net>
>  There is a whole
> network of European geologists who are on the net and a lot of information
> about it is on-line. Granted, not much about its use in growing aquarium
> plants (except for this list), but you will find out a lot if you care to
> look.

James, I'd be interested in some of this material if you can put it
into text form and mail it to me.

> Iron and aluminium are two metals which seem to remain in clays which have
> been subjected to extended weathering over long periods of time. That is
> why a lot of laterite has high concentrations of both.

We can assume that regular clays and probably lateritic clays
contain large proportions of aluminum silicates. Some material I've
been given states that aluminum only becomes toxic (or soluble)
below pH of 5.5 and that in the presence of organic matter, the free
aluminum is rapidly complexed and de-toxified. This suggests that the
whole issue of the presence of aluminum silicates in clays is

Some other points:

Sand, quartz, gravel are all primarily crystalline forms of aluminum

Glass is another form of aluminum silicate and glass vessels can be
used to store some of the most concentrated and powerful acids without