Can anyone tell me what kind of cameo this is ?

Cameos are carved in relief which means they are carved out of the stone they are on. There are also some cameos that are Faux, meaning they have been pasted on a back. Its hard to tell from the picture which you have. Some cameos carved in relief are well made and worth a bit of money. And some cameos that are carved in relief are not well made and perhaps worth less. Best Advice I can give you, it take it to a vintage jewelry flea market or store and ask someone with vintage jewelry experience to look at it for you. Looking at the hardware your cameo is on, it looks to be an older piece. Its worth checking it out!