The seal-ring of the Prophet ﷺ was entirely of silver, its stone being part of it.
حدثنا أحمد بن يونس حدثنا زهير حدثنا حميد الطويل
كان خاتم النبي ﷺ من فضة كله فصه منه
[Sahih] Tirmidhi transmitted it in the Book of Clothing, Chapter on What Is Recommended Regarding the Stone of a Ring, no. 1740, from the hadith of Zuhayr bin Muawiya with this same wording, and he said, hasan sahih gharib. Nasai also transmitted it, no. 5203.