It is glass, but not normal one, it is a strange phenomenon that happens when melting glass at very high temperaturen got put in cold water and solidified very fast in this drop shapes, becoming harder then steel. If you shoot it with a gun, the projectile would be deflected, but this is only true on that round side. If you slightly move the tail all the drop will immediately explode. There are video explaining the phenomenom better than me 😅🤙