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Re: aluminum in laterite

James Purchase wrote:

> Someone also made the statement that "laterite normally contains a large
> amount of aluminium" which can be toxic when present in excess. I don't
> doubt that aluminuim can be nasty when there is too much in the substrate
> but as far as I can tell, true "laterite" does NOT contain a lot of
> aluminium - it has been leached out of the clay by weathering over thousands
> of years of exposure to seasonal rains.

Check your references.  Almost all laterites will contain substantial
amounts of aluminum, primarily as hydroxides, secondarily as the
clays kaolinite and halloysite.  The clays are broken down by weathering,
with near complete removal of silica, sodium and and potassium, but the
iron and aluminum remain behind mostly as hydroxides.

> Many people attempt to save money by
> using a form of bauxite clay in the belief that this is also "laterite". It
> is close, but doesn't deserve a cigar, as it has not had the opportunity to
> have the excess aluminium leached out of it (as has the laterite packaged
> and sold by Dupla).

A) "bauxite" is (I believe) by definition a high-aluminum laterite.
"Clay" sometimes refers to any soil, sediment or rock component less than
2 microns in diameter.  Otherwise, it refers to a class of aluminosilicate
minerals that are (with the likely exception of kaolinite and halloysite)
relatively rare in bauxite.

B) Does Dupla publish a guaranteed analysis of their laterite?  I didn't
know they claimed it to be free of "excess" aluminum (whatever that is).

> I guess its a case of paying 'yer money and taking 'yer
> chances. Dupla Duplarit G is relatively expensive but you don't need a lot,
> and it DOES work.The cost of plants for a tank is usually a lot more than
> the cost of a box of Duplarit.

I'm sure they appreciate your endorsement.

Roger Miller