Vapor Spout is a special block that generates naturally on the surface of Venus.
It is found near the floor of low-lying valleys.
It represents the top or outlet of an underground Sulfuric Acid pocket.
It occasionally emits hot sulfurous yellow vapours which rise up into the Venus atmosphere.
The block can be mined using any pickaxe, but it has little use when mined.
In its naturally spawned position (above a Sulfuric Acid pocket) the Vapor Spout is ideal for placement of a Geothermal Generator.
You can recreate an artificial vapor spout to create energy outside of Venus. All you need to do is to have a bucket of Sulfuric Acid, place the Vapor Spout on top of it (do not replace the liquid), and finally place a Geothermal Generator on top. Unfortunately, it cannot be done in survival, as the vapor spout is only accessible via creative mode.