Branching and Oscillatory Patterns in Plagioclase and Mississippi-Valley Type Sphalerite Deposits

It has been observed for a long time that not all individual minerals have a uniform chemical composition. Many of them exhibit complex growth patterns, such as oscillatory zoning (in which the chemical composition fluctuates along a traverse within the crystal) or branching patterns (characterized by a tree-like crystal form) that arise spontaneously as a result of growth kinetics. Liesegang was among the first to investigate the kinetics of a class of growth patterns: periodic precipitation. Until fairly recently (Lasaga and Kirkpatrick, 1981), the importance of kinetics in geochemistry was largely overlooked.