1. C.A. Sorrell, Minerals of the World, Golden Press, New York (1973).
2. W.C. Roberts, G.R. Rapp, Jr., and J. Weber, Encyclopedia of Minerals, Van Nostrand, New York (1974).
3. L.B. Berry and B. Mason, Mineralogy, Freeman, San Francisco (1959).
4. Hutchinson Ross, Stroudsburg, Penn;K Frye,1981
5. W.A. Deer, R.A. Howie, and J. Zussman, Rock Forming Minerals, vol. 1, Wiley, New York (1962).