Lumium

Lumium is an alloy added by Thermal Foundation. Lumium is used the crafting of many various items, including the Luxduct and Hardened Lumium Glass.

Thermal Foundation
Lumium can be made in Thermal Foundation by mixing Tin, Silver and a bucket of Energized Glowstone.

Then smelt the resulting blend into Lumium ingots.

Ender IO
Ender IO does not add Lumium to the mod itself, but a compatibility recipe is added allowing Lumium to be made in the Alloy Smelter.

Tinkers' Construct
Tinkers' Construct does not add Lumium to the mod itself, but a compatibility recipe is added allowing Lumium to be made in the Smeltery.