This location - a glorious chaos of waterworn sea pebbles - includes a fairly regular instance of conglomerate or spherulitic rhyolite specimens. I have included some similar non-thunderegg specimens below for comparison.
Beautiful Butter-Yellow Black Sea Spherulitic Conglomerate
Black Sea Spherulitic Conglomerate
Larger Black Sea Thunderegg Conglomerate Pebble
Mystery Red and White Black Sea Specimen - Possible Fern Fossil
Simple Black Sea Spherulitic Conglomerate
Larger Black Sea Spherulitic Conglomerate
Large, Pale Black Sea Nodular Mass with Red Agate - Non-Thunderegg