Actinium, discovered in 1899, is the second rarest of the elements. It is a heavy, silvery-white metal that is very radioactive. It has a half-life of 22 years. Samples decay quickly to thorium and francium, making it difficult to determine precise physical properties.

Actinium is obtained as an "impurity" in the pitchblende that is mined for its uranium content. In a ton of pitchblende, one can expect to squeeze about 1/10 of a gram of actinium.

Shown above is a minute quantity (approximately 40 mg) of actinium oxide sealed in a radiaton-resistent quartz tube.

BCIT Chemistry Resource Center
http://nobel.scas.bcit.ca/resource/