Geodes
"A Gift from Mother Nature" - the geode came into being when volcanic bubbles, formed millions of years ago, filled with silicon. This silicon was in an acidic solution which seeped slowly into the bubbles. As the solution dried, the silicon hardened into agate. As the agate formed on the walls of the bubble, it became harder for the solution to penetrate. This, most of the geodes found are hollow centered. As time went by, the lava forming the bubbles was reduced to soil and was washed and blown away, leaving the hard geodes to be found by man.