Holmium - Ho
Discovered in 1878 by P.T. Cleve in Uppsala, Sweden, and independently in Geneva by M. Delafontaine and J-L Soret. Holmium is a member of the lanthanide group and whose properties closely resemble those of erbium and dysprosium. It has an abundance of 1.4 ppm in the earth's crust. It is soft and malleable and is slowly attacked by oxygen and water. It is soluble in acids. Applications for holmium are limited, but it is used as a flux concentrator in magnetic fields and also as a poison in nuclear reactors where it assists in keeping the chain reaction under control.