A pervasive wonder of the natural world is the evolution of varied systems, including stars, planets, minerals, and life—all of which have increased in diversity and patterning over deep time. However, no law of nature describes and explains, much less quantifies and predicts, the behavior of complex evolving systems. Accordingly, our group has proposed a new law of nature, the “law of increasing functional information,” that we apply to the evolution of both abiotic systems (isotopes, minerals) and life. This postulated increase in functional information represents a second arrow of time—one that is consistent with the increase in entropy (the first arrow of time) but is not derivable from the laws of thermodynamics. This concept is now being applied and tested by other groups in fields as wide-ranging as the evolution of languages, the behavior of AI systems, the seasonal variations of soil microbiomes, and the search for new cancer therapies. Mineral evolution, which explores the diversification of Earth’s mineral kingdom on more than 4.5 billion years, is an especially revealing test case of this proposed law of nature.