What do we call a type of body fossil that forms when crystals fill a mold or sediments wash into a mold and harden into rock?

A cast is a specific type of body fossil that is created when sediment or minerals fill the void left by a mold of an organism, hardening into rock and creating a replica of the original shape of that organism. This process typically occurs after the organism's remains decay, leaving an impression or mold behind. When the mold is subsequently filled with material, it takes on the shape of the original organism, providing a three-dimensional representation of it.

Molds, which are formed by the impression left in the sediment where the organism once was, do not themselves represent the actual material of the organism. Instead, they serve as a negative imprint. A fossil trace, on the other hand, refers to indirect evidence of past life, such as footprints, burrows, or feces, rather than a part of the organism itself. Body fossils encompass a broader category that includes both molds and casts, but the question specifically focuses on the process that results in a filled mold, which is defined as a cast.