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
Granite Railway past, many persons were injured — and some killed — while diving into the flooded abandoned quarries from great heights. The Department of Conservation and Recreation maintains the Quincy Quarries Reservation, which has facilities for rock climbing, and trails connecting the remains of the Granite Railway. Granite Railway The Granite Railway was one of the first railroads in the United States, built to carry granite from Quincy, Massachusetts to a dock on the Neponset River in Milton. From there boats carried the heavy stone to Charlestown for construction of the Bunker Hill Monument. The Granite Railway is popularly termed the