Rock is any natural (non-man made) earth
material. It can be biogenic (except made by
man). So coal is a rock, ICE is a rock and
certainly gold is a naturally occurring substance
that is a mineral. Most rocks are made up of more
than one mineral, although monomineralic rocks do
exist. Cement is NOT a rock, plastics are not
rock. I think that rock has to be substantially
solid... so we do not consider water a rock
nor is magma (molten rock) a rock. But when it
solidifies, then indeed it is a rock. Hope this helps.
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