Barium APEX Mineral

Barium (Ba #56) is the next element on the periodic table for my APEX mineral collection.  

Wikipedia Barium
Barium Minerals - The are lots of Barium minerals. 

Witherite (BaCO3) (Barium Carbonate) with 70% Barium is the obvious APEX mineral.    

Barium is very reactive and is extremely difficult to produce without impurities.  Many properties of Barium have not been accurately measured yet.

Barium is found in "Bologna stones". Witches and alchemists were attracted to them because after exposure to light they would glow for years.

Barium has very few industrial uses.  Barium sulfate has a high density and is used in "barium enemas" for imaging contrast.

Barium is not known to be necessary for any living organisms. Barium compounds are poisonous.