Gypsum and anhydrite in the United States, exclusive of Alaska and Hawaii

The distribution of gypsum and anhydrite in the United States (exclusive of Alaska and Hawaii) is shown on the accompanying map. In addition to mines, open pits, and occurrences, the map shows the outcrop patterns of gypsum-bearing fomations and other outlines of the important evaporite basins in which gypsum and anhydrite might be found. Because of the numerous factors involved in determining the amount and purity of the calcium sulfate present in each deposit, no attempt was made to rank the deposits according to size. Deposits of gypsum and anhydrite have not been differentiated on the map.