Mercury is a liquid element with unusually favorable thermal properties. It has a very low specific heat capacity and a relatively high thermal conductivity for a liquid, which makes it effective at moving heat around while changing temperature slowly. Its liquid range is also very wide, from -38.8°C to 356.8°C, so it remains usable across a broad span of temperatures where many other liquids would freeze or boil.
In practice, Mercury is a strong heat-transfer medium and a useful material for building liquid-based systems in extreme environments. Its wide liquid range makes it especially attractive for constructing liquid locks, particularly high-temperature liquid locks, where stability across a large temperature window matters more than availability. When cooled below its freezing point, Mercury solidifies into a form that can be used for buildings operating in deep subzero conditions, below -40°C.
Mercury also has a default element mass of 600 kg, which is important when considering storage, piping, and temperature buffering. Because it combines decent thermal conductivity with a low heat capacity, it can move heat efficiently without absorbing as much of it as many other liquids. That makes it useful anywhere a player wants the liquid itself to stay relatively stable while still exchanging heat with surrounding systems.
A separate use is lighting: Mercury can be consumed by a building that provides strong illumination to the area directly beneath it, at comparatively low power consumption. This makes it a specialized light source for targeted coverage rather than general base lighting.
Mercury is one of the few liquids with a very wide temperature window, letting it function in both hot and cold systems.
Its low specific heat means it is not ideal when large heat storage is needed, but it is effective when fast heat transfer is the goal.
It is especially practical for liquid locks in high-temperature areas because it resists phase change across a broad range.
When frozen, it becomes a solid material suitable for deep-freeze building applications.
Before version 207167, a bug could cause the top of the world to unexpectedly turn into a massive pool of Mercury, generating liquid in many places and causing severe performance drops. This was the only time Mercury appeared outside Creative Mode before the game’s full release.
