Densinium Ore

Densinium Ore is a tier 6 ore. It can be found on Cyber Spheres, Gas Giants and (in small quantities) on Sulphuric planets. It slightly glows in the dark, so you can notice it even without Ore Detector.

Note that this ore is very scarce near the surface. Underground layers of the planet will have significantly more of it.

Densinium, while has many useful applications in many game aspects, can't be obtained anyhow besides from direct searching and mining it on the listed planets. It makes this material one of the most valuable and rare - majority of other ore types can be produced without direct mining.

Block durability bonus
Densinium Ore increases hitpoints of the block by 62. If your base is suffering from damaging weather (such as Cosmic Blasts), you can use Material Mod Placer to add Densinium Ore to the blocks that need extra durability. Alternatives: 1) tile protection from Field Generator, 2) using already sturdy blocks like Diamond Block.

While other ores also add hitpoints to blocks, their bonus is very low in comparison (18 hitpoints for Penumbrite Ore and Plasmic Crystal, 30 for Trianglium Ore, below 10 for most other ores).