The seal of the Prophet ﷺ was made of silver, and its stone was part of it.
أخبرنا أحمد بن سليمان قال حدثنا موسى بن داود قال حدثنا زهير بن معاوية عن حميد
كان خاتم النبي ﷺ من فضة فصه منه
[Sahih] Reported by Abu Dawud, chapter on the ring, section on adopting a ring, no. 4217, and Tirmidhi, chapter on clothing, section on what is recommended regarding the stone of rings, no. 1740, from the hadith of Zuhayr bin Muawiya through this route, and he said, "hasan sahih gharib." It is also in al-Kubra, no. 9518, and see the previous hadith.