Am not a jewelry expert, but have been wearing black onyx jewelry, sterling silver jewelry, and various ear studs for years. These do appear to me to be onyx, and they also do appear to be sterling silver.  Other inexpensive studs I've purchased at Amazon from other sellers claimed to be stone and/or sterling, but definitely were not. Am very happy with these and plan on buying more from this seller, as they have an excellent selection of studs in the 6mm size, which I prefer.