What does ivory stone look like? And is it very rare or expensive?

Ivory is not actually a stone, but rather the name given
to the bone-like material that forms the bulk of elephant's tusks.  In essence, it is
similar in both substance and appearance to your own teeth!  And just like teeth, ivory
varies in color from yellow to very bright white.

Ivory has
been prized (that is, expensive) throughout history for its value in both art and
manufacturing.  Intricate sculptures and carvings made from ivory have been found dating
back to ancient times.  More recently ivory was used to make billiard balls, piano keys,
and other items before the invention of plastics.

Ivory is
now rarer than ever.  Driven by the high price of ivory, the hunting of elephants for
their tusks has resulted in a terrible population decline a to the wholesale slaughter
of the American bison during the 1800s.  Many countries have banned the sale or import
of ivory.  However, illegal poaching of elephants continues in many parts of the world,
and the future of elephants is uncertain.