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Re: Oregonn laterite

On Wed, 15 Mar 2000, Robert H. wrote:

> Thats interesting James..(and I am not going to get sucked into this
> argument again!) but it seems to be talking about lateric rock formations,
> not lateric soil...

From reading the abstract it looks like the laterites in question are what
are called "paleosols".  Layers of ancient soils that were buried and
preserved.  The authors say the laterites formed before an event in the
early Pliocene epoch, which would (according to the pretty geologic time
chart on my office wall) make them 5+ million years old.

That's awfully old dirt, but pretty young as rocks go.  Age might not have
that much to do with it though because laterites (even those in modern
soils) are often rock-hard.  I think that's why some laterite products
are granular, rather than powdery.  They're probably rather rock-like to
start with, then they're just crushed and sized for sale.

The abstract also describes the laterite as "high-silica laterite" which
implies to me that they probably have a higher clay mineral content than
is common for laterites.  That description makes them sound very similar
to some of the red soils in the SE US, which I've seen described in
technical literature as "lateroid"  soils.

Those paleosol laterites might work for aquarium use, but before y'all in
the Portland area go digging up your hillsides you should probably see if
the report includes a chemical analysis of the laterites.  Most laterites
are predominantly aluminum hydroxides with enough iron to make them red,
but perhaps not enough iron to be particularly good in your tank.

Roger Miller