Water-insoluble aluminosilicates as tanning agents for the dressing of fur skin

In the process of tanning for the production of dressed fur skins comprising subjecting pickled fur skins to the action of an aqueous liquor containing tanning agents, the improvement which comprises adding to the pickling bath as sole tanning agent a water-insoluble aluminosilicate, containing bound water, of the formula (Cat2/nO)x .Al2O3.(SiO2)y wherein Cat represents a cation selected from the group consisting of alkali metals, bivalent metal ions, trivalent metal ions and mixtures thereof; n represents an integer from 1 to 3; or x is a number of from 0.5 to 1.8; and y is a number of from 0.8 to 50, said aluminosilicates having an average particle size in the range of from 0.1 mu to 5 mm and a calcium binding power of from 0 to 200 mg CaO/gm of anhydrous active substance measured at 22 DEG C. according to the Calcium Binding Power Test Method.