Who wants a heart of stone? Right. No one.
But here it is anyway.
The basic shape was created with a script in OpenSCAD.
OpenSCAD is free software: https://openscad.org/
The 2024 version of OpenSCAD was used with optimizations turned on. The 2021 version of OpenSCAD is too slow with this script.
The result of the script in OpenSCAD is this shape:
The basic shape was then processed in Blender with smooth, voxel remesh, and displacement map:
The blue heart is printed with PLA with tree (organic) support with the support only on the build plate. The two other pictures are renders.
The license for the script and the resulting stl files are CC0 (Public Domain).
The author marked this model as their own original creation.