ancient doll

Hello I was digging around marines shop and found some Ancient dolls now I have 3 dolls and idk what to do with them I don’t want to throw them away since they seem kinda rare

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