Check out the Giant Crystal Caves

The picture above is a rock called Gypsum. When we
were in Coober Pedy (known for its opal mining), we went
noodling (looking around the piles of dirt brought out
from the mines) for opal. We didn't find much opal, but
we did find some beautiful crystal rocks called gypsum.
It breaks easily into fine, needle-like strands.