It probably has a rocky core, then a layer of mixed rock and ice above that.

它很可能有一个岩制核，被一层岩石和冰的混合物包裹。

George had mixed a sharp rock in the dirt and it bruised her knuckles.

乔治在泥土里混了一块锋利的石头， 砸伤了她的指关节。