Paul E. Lehmann Wrote:
> Sand, Silt, and clay are terms used to describe SIZE of particles and
> not composition.
You are correct that in soil science they define these things by the
size of the particles. But that doesn't exclude what I said, at least
in a practical and broad sense.
Most rocks contain a lot of silicate minerals and/or a lot of silica
grains, so in practice the sand in your garden soil will be mostly
silica, or at least a source of silica. Things might be different if
you are gardening on a volcanic soil, or the spoil heap of a mine,
etc.
Silt can be formed by mechanical weathering, but to get clay we need
chemical weathering. So clay (meaning small size soil particles) will
reliably be clay (meaning one of a range of aluminium phyllosilicate
minerals).
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echinosum
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