Etharium

An amazing, enchanted mineral that forms and attracts a breathable atmosphere twenty times is volume. A 1' diameter sphere of pure Etharium will create a 20' diameter sphere of atmosphere. Due to its enchanted nature, Etharium performs the same even under pressure (underwater).
Etharium is found naturally and in large quantities on nearly every planetoid. It can be a pure concentration (the most valuable) or more commonly found in other rocks. It is blended in to sedimentary rocks, found as pure intrusive bands in metamorphic rock as well as mixed in with other types of minerals in igneous type rocks.
Etharium is typically used on a solarship or submersible to maintain an atmosphere where none exists.
Etharium is recharged by being on the prime material plane and exposed to direct or indirect sunlight.

When removed from the Prime Material Plane, Etharium loses its ability to produce an atmosphere and recharge.