Mineral alkali metals, behavior

Rubidium is a silvery white and very soft metal that colors a flame yeUowish-violet. In chemical behavior rubidium resembles sodium and potassium and reacts violently with water. It is a widely distributed element, usually associated with other alkali metals in minerals. The rate of radioactive decay of the isotope Rb can be used in geological age determination (see Chapter 4 Geochemistry). Rubidium is found in small quantities in tea, coffee, tobacco and other plants. 

Alkali metals occur in salty coals typically as chlorides, humates, sulfates, and carbonates. The reducing atmosphere in the gasifier favors the continuous liberation of volatile minerals, resulting in steadily changing eutectics causing transitions of the ash fusion behavior, which are nearly unpredictable. 

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