Granite may have more alkali feldspar, whereas a granite derived from partial melting of metaigneous rocks may be richer in plagioclase. It is on this basis that the modern "alphabet" classification schemes are based. The letter-based Chappell & White classification system was proposed initially to divide granites into I-type (igneous source) granite and S-type (sedimentary sources). Both types are produced by partial melting of crustal rocks, either metaigneous rocks or metasedimentary rocks. M-type granite was later proposed to cover those granites that were clearly sourced from crystallized mafic magmas, generally sourced from the mantle. However, this proposal has been rejected by
California Coastal Comm'n v. Granite Rock Co. largest in California, and the largest west of the Rocky Mountains. In 1980, Granite Rock submitted to the Forest Service a five-year plan to remove substantial amounts of limestone from a quarry on the south face of Pico Blanco within the National Forest boundary. The Forest Service prepared an Environmental Assessment of the plan and recommended some modifications, which Granite Rock implemented. When Graniterock obtained the permit in 1983, it began to excavate a open pit mine. The California Coastal Commission required Granite Rock to apply for a coastal development permit for any mining undertaken after the date of notification.