Marshite (CuI) (Copper Iodide) with 67% Iodine is my obvious APEX mineral. It is only found as inclusions in other minerals. All Iodine Minerals are salts so it does not completely satisfy my APEX Mineral definition.
Iodine is a relatively rare element in the universe. It is a dark solid that sublimates easily at 114 °C into a purple gas. The main sources of Iodine are the caliche (desert rocks with brine deposits) of Chile and the gas/oil brines of the USA.
Iodineand its compounds were unknown before modern times.
Iodine is mainly manufactured for use in dietary supplements for people and animals.
Iodine is the heaviest essential element utilized widely by life. There are many Iodine deficiency problems in land animals and inland human populations because of its scarcity. Only Tungsten, employed in enzymes by a few species of bacteria, is heavier.