Lithium

Lithium (Li), element 3. The softest and least dense of all metals. Often found dissolved in seawater or in pegmatite deposits, especially near thermal vents. Useful in lubricants, batteries, advanced glass, nano-welding, quantum physics, and anti-aging drugs. Also a budget air-cleaning element on spacecraft. Lithium’s role in this world’s biosphere is unknown. In humans it has historically been used as an antidepressant. Despite the advent of cognitive connectome therapy, lithium is still used as a folk remedy on some worlds, despite the risk of permanent side effects.