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 Rock Township, Redwood County, Minnesota was $35,000, and the median income for a family was $37,250. Males had a median income of $30,625 versus $20,500 for females. The per capita income for the township was $12,631. About 8.2% of families and 12.1% of the population were below the poverty line, including 15.0% of those under the age of eighteen and 6.5% of those sixty five or over. Granite Rock Township, Redwood County, Minnesota Granite Rock Township is one of the twenty-six townships of Redwood County, Minnesota, United States. The population was 241 at the 2000 census. Granite Rock Township was organized in 1890, and named