Cobalt!

The Periodic Table of Elements has some random "What the-!?" elements on it. Sometimes Hema'ehu looks at a certain element name and thinks, "Is that even real?" Cobalt falls into that category, for although it is a most excellent color for a cocktail shaker there is little that we know that makes cobalt "useful."

Turns out there are two legitimatizing biological needs for cobalt: Vitamin B12 and nitrogen fixation.

Vitamin B12 is an essential nutrient. We use it for cool things like extracting energy from proteins and fats - that is, burning your body's fuel to function. Cyanocobalamin, in the parlance of chemistry, is also a large, unwieldy compound that can't be formed by plants or animals. Notably, this vital, life-would-cease-to-exist-without-it nutrient is synthesized by micro-organisms only: Bacteria and Archaea 1; higher plants and animals 0.

Nitrogen, which is utilized extensively by plants in cell construction and photosynthesis, is plentiful in the atmosphere (78% of it, in fact) but in the biologically inert form of di-nitrogen N2. Some plants - like legumes or Ceanothus - have convinced microbes to live on/within roots and transform N2 into active forms of Nitrogen in exchange for carbohydrates or energy. These symbioses tend to benefit both the plant and the microbe; one recieves an otherwise limiting nutrient (Nitrogen) and the other recieves a steady source of sustenance.

Without Cobalt, none of this happens. We're sorry Cobalt, we had no idea... we were just joking about the "useless" barb. Please don't hurt us.