This report is one of a series (Groat et al. 1994, 1995a, 1995b, 1996) on the results of research on granitic pegmatites in northwestern Canada. These unusual rocks are of scientific and economic interest for the following reasons:
1) Rare elements such as Ta, Nb, Li, Rb, Cs, Be, and Sn are commonly found in granitic pegmatites, and can occur in concentrations sufficiently high to warrrant mining operations (e.g. Bernic Lake, Manitoba). Tantalum and niobium are used in prostheses, capacitors, laser crystals, and piezoelectric instruments; lithium is medicinally important for the treatment of manic depression, is used in advanced technology batteries, and is a key ingredient of specialized glassware; and beryllium and tin are industrially important as components of alloys.
2) Granitic pegmatites host a diversity of rare mineral species, and are a globally important source of gemstones such as emerald, topaz, aquamarine and tourmaline. Pegmatites in western North America have known gemstone potential.
3) Granitic pegmatites reveal information about melting of rocks in the lower crust and are an important source of information regarding fractionation of felsic magma suites, especially extreme fractionation. The minerals from granitic pegmatites were among the first to be used in absolute (radiometric) dating; granitic pegmatites are of importance in relative and absolute dating of the late stages of tectonic events.