This agate specimen is an enhydro, which means that there is a cavity inside the agate where water is trapped! If you shake this piece near your ear, you can hear the water inside. Enhydros are on the rare side and can form inside of a large variety of minerals, crystals, and gems. This is an absolutely natural occurrence and is not man made, however the agate's surface had been polished for a lovely shine and comfortable feel in the hand.A very fun piece to add to your collection!