Certain hexahydroindan-2,2-diphosphonic acids useful in treating diseases associated with abnormal calcium and phosphate metabolism

A hexahydroindan diphosphonic acid having the following structure:

• ##STR9## wherein R.sub.1 is one substituent selected from the group consisting of hydrogen, unsubstituted or substituted saturated alkyl having 1 to 6 carbon atoms, unsubstituted or substituted unsaturated alkyl having 2 to 6 carbon atoms, unsubstituted or substituted phenyl, unsubstituted or substituted naphthyl, unsubstituted or substituted benzyl, hydroxy, halogen, amino or amido, wherein substituted represents a substituent selected from the group consisting of methyl, methoxy, hydroxy, chloro, methylamino, dimethylamino or diethylamino, or a pharmaceutically acceptable salt thereof.