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
Fall River granite of the underlying granite is the Hixville Fault near Dartmouth, Massachusetts. From a distance, the rock exhibits a distinctive tan-gray color. Viewed up close, it is more pink. The granite is very hard and durable, but cannot be polished very well. As a result, its appearance on a building is almost always somewhat rough, rather than the sharp lines of other types of building stone. Edmund Hitchcock, of the 1841 Geological Survey of Massachusetts gave the following description of the granite: But no rock can be finer for architectural purposes than the granite of Troy...The feldspar of this rock is