ancient doll

I'm on switch version 1.6.9 build 37, and when I dropped an ancient doll in the volcano caldera lava, nothing happened. I took off my magnet ring, opened my inventory, threw the doll out, it sat there for a second then fell in with a splash but I did not get the far away stone. Did I do it wrong...

Im in level 100 in the mines and i have 2 ancient dolls but i can't throw either into the lava