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. of activities on federal lands. Granite Rock Company of Watsonville, California purchased the property and mineral rights to a large deposit of white limestone on Mount Pico Blanco in the Los Padres National Forest on the Big Sur coast of California in 1963. The limestone deposit is made up of two large, pharmaceutical grade limestone bodies known as the Pico Blanco body and the Hayfield body. It is the only high-grade deposit on the Pacific Coast outside Alaska within three miles of potential marine transportation. Reserves have been estimated to be from 600 million to a billion tons, reportedly the