The seal-ring of the Prophet ﷺ was made of silver, and its stone was Abyssinian.
حدثنا قتيبة وغير واحد عن عبد الله بن وهب عن يونس عن ابن شهاب
كان خاتم النبي ﷺ من ورق وكان فصه حبشيا
Agreed upon. Muslim narrated it in the Book of Clothing and Adornment, chapter on the silver ring with an Abyssinian stone, hadith 2094, from the hadith of Ibn Wahb, and Bukhari, hadith 5868, from the hadith of Yunus, with the same wording.On this topic there is also a hadith from Ibn Umar [Tirmidhi in Shamail, hadith 100] and from Burayda [coming up, 1785].