Didn't want to start a new thread for this, so combed through the forum for a suitable existing thread.
Dateline: San Salvador (Columbus Island), Bahamas, about 1993. I was a speaker at a wine event in the Club Med and found this conch shell on the beach?even impressed a few guests, as a former trombonist, in making it sound reasonably well. It's been sitting on the upstairs bathroom sink all these years, without a second thought.
Moved it for cleaning the other day and heard a small rattle. Shook it, and the 'calcareous concretion' as shown popped out. Apparently over the years it had dried/shrunk enough to become dislodged.
Photos show the hole through which the animal had been harvested for consumption, also a closeup of a parasite bore hole that would be the likely origin of the concretion.
Although CIBJO may define this as a (non-nacreous) pearl, I would withhold that designation for a calcareous concretion of greater beauty.
Still, it goes to show that one should shake their conchs more frequently?