Here's a breakdown:
* Hard part: This refers to a solid structure within an organism, like a bone, shell, or tooth.
* Dissolves: Over time, these hard parts can be broken down and dissolved by chemical processes (like weathering or acidic water).
* Mold: The resulting empty space in the rock is the mold. It's a negative impression of the original hard part.
Example: If a seashell gets buried in sediment and then dissolves away, the remaining space in the rock is a mold of that seashell.
