| Reference | {Deposit:: MICHIGA* INDUSTRIAL SAND RESOURCES, 2000, CIRCULAR 11, GEOLOGICAL SURVEY DIVISION, LANSING, MICHIGAN.}{Deposit:: HEINRICH, E.W, 1979, ECONOMIC GEOLOGY OF THE SAND AND SANDSTONE RESOURCES OF MICHIGAN, GEOLOGICAL SURVEY DIVISION, LANSING, MICHIGAN.}{Deposit:: U.S. SILICA COMPANY WEB PAGE, http://www.u-s-silica.com/rockwood.html} |