Frog charms

There are 3 missing black stones on 1, & 1 on the other. Not sure value, if real onyx, or anything about them but I’ve had over 20 years, & they were given to me so I have no idea if antique or?? Found similar items on google & ebay while trying to figure out. They are definitely some sort of metal, silver, unsure? I used a couple times. Once i clipped on black heels, another on my bag, & once on a scarf. Could be anything?