It just looks like some type of calcite formation. A lot of things in mollusc fossils can look like it was a pearl. Even if it is a fossil pearl(very, very doubtful in this case), it is no longer technically a pearl. After a mollusc dies and depending on its final resting place, nature immediately starts recycling it into something different through things like moisture, mineral infiltration, temperature, pressure...etc, even though it may appear "preserved".
Slraep