Investigations of predominantly Tertiary age bentonite deposits in the far western states show that these bentonites are primarily of the Ca and Ca-Na intermediate types. High Na bentonites in Tertiary formations are rare but do occur in isolated instances. Almost all of the bentonite deposits examined have viscosities of less than 70 bbl/ton and water loss in excess of 20 ml. This would indicate their main use to be as pond or reservoir sealants, pet adsorbents and animal feed binders. The available tonnages of these bentonitic materials are large, and in most cases, are heavily located by mining claims.
The bentonite deposits also have large amounts of other mineral phases, mainly zeolites, silica minerals, feldspar minerals and gypsum. In some cases, sepiolite also occurs, especially in areas suspect of any hydrothermal activity. Zeolites, chiefly cl inoptilolite, are so common in the Tertiary age bentonites that in some deposits, the claimants were mining and selling zeolites instead of bentonite. In these deposits the claimants were of the belief that they were selling bentonite. This would indicate that zeolites apparently can substitute or at least are suited to the same uses as Ca or intermediate Ca-Na bentonites.