Hi Anthony,
The criteria that you mention below are not enough.
Many limestones have sedimentary layering, and some
sandstones lack it (though absence of layering combined
with a dense creamy consistency is often a marker for
limestones.
We geologists use three testing methods. The first is
to put a drop of dilute Hydrochloric acid on the surface
and see if it fizzes. This is a good test for the
mineral calcite (calcium carbonate) of which most
limestones are made. Beware, though; some sandstones
contain a natural calcite cement. They will fizz like a
limestone.
Or look closely with a x10 magnifier. Often the quartz
grains of a sandstone will be clearly visible as greyish
or brownish, slightly translucent grains.
But the best way by far, and the one that distinguishes
the true stone-lover from the fastidious dilettante <:)>
is to scrape a minute flake of the stone off a fresh
clean surface and to nibble it between the front teeth.
Limestones are slightly crunchy but soon break down into
a smooth paste. The quartz grains in a sandstone are
much harder and will take much more of a bite to crush
them. Sometimes they will even squeak a bit as you
chew. Do a comparison once between a known sandstone
and a known limestone and you will immediately
experience the difference.
Of course there is no guarantee that bits of tooth edge
will not occasionally spall off (only on sandstones:
never on limestones), but most geologists over here in
England have no worse teeth than non-geological
Englishmen...
Tim
At 13:27 28/03/00 -0500, you wrote:
>I was wondering if anybody can tell me if there is a
>surefire way to tell the difference between limestone
>and sandstone just by looking ...
Dr Tim Palmer C.Geol., F.G.S.
Executive Officer, The Palaeontological Association
I.G.E.S., University of Wales
Aberystwyth SY23 3DB
Wales, U.K.
E-mail: palass[AT]palass.org
Web: www.palass.org
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