Name:   Muscovite-Biotite Granite

Geologic Name:  Concord Granite

Reference:  Dale, T.N., The chief commercial granites of Massachusetts, New Hampshire,
and Rhode Island:  U.S. Geol. Survey Bull. 534, p. 145-156, 1908.

Microscopic characters:  Granitic texture.  Composed of quartz showing undulatory
extinction and containing hair-like inclusions of rutile, orthoclase and sodic plagioclase
partially altered to sericite, fresh microcline showing lattice structure, biotite with
abundant pleochroic halos and muscovite.  Accessory minerals are apatite, zircon, rutile,
and magnetite.