Other common rubidium compounds are the corrosive rubidium hydroxide ( RbOH ) , the starting material for most rubidium-based chemical processes ; rubidium carbonate ( Rb2CO3 ) , which is used in some optical glasses , and rubidium copper sulfate , Rb2SO4 · CuSO4 · 6H2O .
Rubidium chloride is the most common rubidium compound .