Obsidian

Obsidian is a raw mineral used primarily as a construction and industrial material. It is found across world generation in varying amounts, and is especially common on worlds with the Boulders World Trait and on The Badlands Asteroid. It can also be harvested from renewable Space POIs during rocket missions, especially in Metallic Asteroid Fields, where it is produced at a rate of 378–1134 kg per cycle.

Its main value comes from its thermal properties rather than its décor value. Obsidian has low specific heat capacity, high thermal conductivity, and the Thermally Reactive trait, which makes it an effective heat conductor. In practice, this lets it move heat quickly between areas and objects in contact with it. It also has a very high melting point, allowing it to survive conditions that would destroy many other common building materials. This makes it useful for structures exposed to extreme temperatures, including tiles and ladders placed in or near magma, volcano containment, and pipes that are difficult to melt.

Despite these strengths, Obsidian has limited use compared with other rocks. It provides no decor bonus, so it is usually a worse choice than sandstone or granite when building items where décor matters. Its strongest uses are mostly situational and tied to its heat resistance and thermal conductivity.

• Marble Block requires 400 kg of Granite or Obsidian, though Granite is usually preferred because it gives a 20% decor bonus while Obsidian does not.
• Monument Base requires 2500 kg of Obsidian in addition to Steel.
• Rock Crusher can crush 100 kg of Obsidian into 100 kg of Sand.
• Stone Hatches can eat Obsidian and produce Coal.
• Shove Voles cannot burrow through tiles made of Obsidian.
• It has the highest radiation absorption rate among raw minerals, tied with Igneous Rock.

Obsidian’s abundance can differ dramatically from one world to another, so players often treat it as either a common construction stone or a scarce specialized resource depending on the map. Because of its high melting point and good thermal conductivity, it is often saved for projects where ordinary rock would fail, rather than used broadly for everyday construction.

In earlier versions of the game, Obsidian had a much lower hardness value, around 50–80 instead of its current 200.