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
Dedham Granite notable building projects in and around Dedham. It was used for St. Mary's Church (1880), St. Paul's Church (1858), Memorial Hall (1868), the Boston and Providence Railroad station (1882), the Dedham Public Library (1888), Trinity Church in Copley Square. There are several pieces of it arraigned decoratively along East Street in Dedham, between High and Avery Streets. These pieces were remnants of the railroad abutment that was dismantled in 2008. Plymouth Rock is also a piece of Dedham Granite, having been moved to the coast by a glacier 20,000 years ago. Dedham Granite Dedham Granite is a light grayish-pink to