Solinium

Solinium a Schrabidium isotope (Sa327), not to be confused with the regular isotope cyan-blue Sa326. The reason you've probably haven't heard a lot about it is that to be frank, it's trash compared to its isotope sibling. This is because unlike Sa326, an extraordinarily powerful fissile element, it is not fissile nor is it even fertile (in the traditional sense).

It yields 80 operations in a breeding reactor with 3 HEAT, and 400 in the nuclear furnace, which is one of its only good uses. It isn't of much utility, you can use it in a Schrabidium-like bomb. Solinium can be in the form of rods, nuggets, ingots, and blocks, but the rod is what's most commonly used (nuclear furnace, breeding reactor operations, and Euphemium production), ingots and blocks don't have much use apart from taking less space in item storage.

It causes the same blindness effect as regular Schrabidium.

Production
Primarily a (presumed) decay element from Schrabidium fuel (or perhaps a Schrabidium-326 neutron capture product). It can also be extracted from Schrabidium Clusters from Schrabidium that failed to turn into Euphemium.

Can be obtained from Poisonous Mud, the waste product of the Watz Plant, also as a presumed decay/neutron capture element.

It can be bred from Schrabidium in a Breeding Reactor, though that would probably count as a waste.

Uses
Somewhat decent Breeder fuel with 3 HEAT and high operation count.

Solinium quad rods can be bred to transform it to "Burned Out Schrabidium Quad Rods" by breeding it in the breeding reactor which can be crafted into Euphemium nugget. They do not stack. This method is not particularly efficient but can be useful if you have no use for waste Solinium as breeder fuel.

It can also be used in the bomb "The Blue Rinse".