Silicate minerals, constituting more than 90% of the rocks exposed at the earth’s surface, are commonly formed under temperature and pressure conditions that make them inherently unstable in surficial environments. Undoubtedly, the most significant aspect of chemical weathering resulting from this instability is the formation of soils which makes life possible on the surface of the earth. Many soil macronutrients in this “critical zone” are directly related to the rate at which primary minerals weather (Huntington, 1995; Chadwick et al., 2003). Chemical weathering also creates economically significant ore deposits, such as those for Al and U (Samma, 1986; Misra, 2000), as well as potentially releasing high concentrations of toxic trace elements such as Se and As (Frankenberger and Benson, 1994). Silicate weathering is a significant buffer to acidification caused by atmospheric deposition (Driscoll et al., 1989) and from land use practices (Farley and Werritty, 1989). Atmospheric CO2 levels have been primarily controlled by the balance between silicate weathering and the rate of volcanic inputs from the Earth’s interior, a relationship which may explain long-term climate stability (Ruddiman, 1997)
