The Stone Egg has three states, normal, overheated, and freezing. The Stone Egg grows while it is normal, and slowly shrinks when it is overheated or freezing. During the Night, the Egg will be freezing unless being placed closed to a Fire, but during the Day, it will overheat if too close to a Fire.
The Stone Egg was added during the Early Access phase of Hamlet.
Storing the Stone Egg in a Chest will cause multiple Ro Bins and Gizzard Stones to spawn.
The Stone Egg can be brought outside of Hamlet by using the Skyworthy.
A Stone Egg found at the BFB's nest.
An overheated Stone Egg after it's been placed by a Fire Pit.