Lead. Here is a weight used by divers on
their belts. You can see you can put a
loop a belt through this and you have
several of these to counterbalance the
buoyancy for scuba divers. Lead is very
heavy. We all know that interestingly
enough lead is not as heavy as gold is,
and as a result it is very difficult to
fake gold by simply painting over, because
one can determine the density of this
and show that indeed it is an element
other than gold, such as lead. The
Archimedes principle utilizes this, the
idea of buoyancy, and the displacement
and of course Archimedes himself was the
person who jumped up from his bathtub, so
the story goes, once he had the idea of
how to ascertain whether or not the
king's crown was pure gold or whether it
was fake. Lead ore, typically in the form
of Galena, which is lead sulfide notice
this crystal is cubic, very similar to
the iron sulfide. This is heavy as well
because it is a lead compound. Most of
the lead is obtained from lead sulfide
in the world's metal business. Here is a sample
of Cerussite. Cerussite is lead
carbonate and it is white. Now this was
used very commonly for paints up until
several decades ago, because it is a
beautiful white pigment for paints; and
of course is poisonous; and we have
phased out of Cerussite or lead
carbonate to titanium oxide instead.
Actually lead can occur in the native
state
here's a sample here of native lead, and
if you remember I said a few moments ago,
it was confused sometimes
by the ancients with graphite; and, indeed
it does look like graphite, doesn't it?
But it is heavier than graphite, but back
several centuries ago scientists or
alchemists were not concerned with
density as they are today.
