This Bureau of Mines publication estimates that U.S. Helium resources as of January 1977 were 710 billion cubic feet. These resources are broken down into four classifications, as follows: helium in measured natural gas resources and in storage, 201 billion cubic feet; helium in indicated natural gas resources, 150 billion cubic feet; helium in hypothetical natural gas resources, 175 billion cubic feet; and helium in speculative natural gas resources, 184 billion cubic feet. Most of the helium in natural gas is presently dissipated when natural gas is consumed as fuel and for other purposes. Helium resources of the United States may also be divided into three other categories: (1) depleting and undiscovered natural gas resources, 589 billion cubic feet; (2) nondepleting natural gas, 83 billion cubic feet; and (3) storage, 38 billion cubic feet, of which 37 billion cubic feet is federally owned and 1 billion cubic feet is privately owned. The United States does not have any significant leasehold rights in the depleting fuel gas resources. However, through the Department of the Interior, it does have leasehold rights to about 70 percent of the helium found in nondepleting natural gas, and it owns over 90 percent of the helium in storage.