Short answers, pulled from the story.
Sir Humphry Davy first isolated barium in 1808 in England, using electrolysis of molten barium salts. He named the element after "baryta," the alchemical term for barium oxide, adding the "-ium" ending that denotes a metallic element.
The two main minerals are baryte (barium sulfate, BaSO4) and witherite (barium carbonate, BaCO3). Major baryte deposits are found in many parts of the world, with China producing more than 50 percent of global output; main witherite deposits are located in Britain, Romania, and the former USSR.
Barium sulfate has low toxicity and a relatively high density of approximately 4.5 grams per cubic centimeter, making it opaque to X-rays while safe to ingest. It was first applied as a radiocontrast agent in X-ray imaging of the digestive system in 1908.
Water-soluble barium compounds are poisonous and have been used as rodenticides, with barium carbonate being one example. Insoluble barium compounds such as barium sulfate are nontoxic and not classified as dangerous goods. The US EPA considers it unlikely that barium causes cancer when consumed orally.
Barium nitrate imparts a yellow or apple-green color to fireworks when no chlorine donors are present. When chlorine donors are used, barium chloride forms in the reaction and generates emerald greens.
Barium is a component of YBCO, the first high-temperature superconductor cooled by liquid nitrogen. YBCO has a superconducting transition temperature of 93 K, which exceeds the boiling point of nitrogen at 77 K, making liquid-nitrogen cooling practical.