This specimen is from the Hauck Collection. It is a huge, hollow sphere of coral - you can clearly see the pattern on the outside - that has been replaced or filled inside with botryoidal chalcedony - one of those unusual cases where biology meets mineralogy. The coral is flat on the bottom, where it was attached, and almost perfectly spherical on top, like a skull. Amongst the botryoidal forms of the chalcedony inside are stalactitic "fingers." Some of the chalcedony is white, and some of it is a translucent coffee color.