The 'other' Polish thunderegg location, but far far rarer than Nowy Kościół. They are similar, with a highly granular matrix - but distinguished by a darker tone to the whole egg, and by a much greater tendency to translucent agate in deep wines and greys. That makes them stunningly beautiful if you are lucky enough to track down a higher-end specimen.
Magnificent Sokolwiecz Thunderegg with Banded Agate