Tungsten Ore

Tungsten Ore can be found on most tier 2-2.4 planets, including the Desert and Forest planets in the starting system.

It exists in great quantities on some Mountainous planets (note that other Mountainous planets are tier 2.5+, and they won't have Tungsten at all).

Tungsten Ore can also be created from ingredients available on your starting planet using your furnace. However, to gain the ability to do so requires you to have a piece of Tungsten Ore to learn how to do it, so Tungsten is not available until you've left your starting planet.