Obsidian

Obsidian is a raw mineral in Oxygen Not Included used primarily as a construction material and as a harvestable resource on Space POIs. It appears in certain biomes and asteroid POIs and can be obtained in large quantities from Metallic Asteroid Fields on rocket missions, where it yields 378–1134 kg per cycle from renewable Space POIs. World generation and traits strongly affect its availability: it is most common on worlds with the Boulders World Trait and is especially abundant on The Badlands Asteroid.

As a building material, Obsidian is defined by its thermal properties rather than by decoration. It has a low specific heat, high thermal conductivity, and the Thermally Reactive trait, which makes it an efficient conductor that rapidly changes temperature and encourages heat transfer between adjacent tiles and structures. Obsidian also has a very high melting point compared to most natural rocks and metals, allowing it to be used for structures that must resist Magma temperatures — for example, ladders, tiles, or containment walls exposed to volcanoes or direct Magma contact. Obsidian does not provide any Decor bonus, so it is inferior to Granite and Sandstone when Decor is a consideration.

Practical gameplay interactions and uses:

• Obsidian can be consumed by Stone Hatches as food; Stone Hatches excrete Coal when fed Obsidian.
• The Monument Base requires 2500 kg of Obsidian (in addition to Steel) as one of its construction materials.
• Marble Block recipes accept 400 kg Granite or Obsidian to create a Marble Block.
• A Rock Crusher can crush 100 kg Obsidian into 100 kg Sand, providing a way to convert excess Obsidian into Sand.
• Shove Voles cannot burrow through tiles made of Obsidian, making it useful for pest containment.
• Obsidian shares the highest Radiation Absorption among Raw Minerals, tied with Igneous Rock.
• Because Obsidian lacks the 20% Decor bonus that Granite provides, Granite is often preferred over Obsidian for decorative or sculptural construction when both are available.

Historical note: Obsidian’s hardness was changed during development; early versions assigned it a hardness around 50–80, while in current versions it has a hardness of 200.