It has been established that in kimberlite rocks fresh groundwaters with the content of total dissolved solids of 0.5- -0.6 g/dm3 are characterized with the sodium hydrocarbonate and sodium chloride-hydrocarbonate compositions; with a high content (about 80 %) of sodium and potassium (Na+K); and with the high рН factor (8--9.2). Waters of similar compositions are observed in rocks containing and overlapping kimberlite pipes. Such features of underground waters are connected with the processes of hypergenic serpentinization and saponitization of the kimberlite rocks, and with the hydrolysis of sodium aluminosilicates. Apart from that, there observed the cation exchange of sodium in the rocks for calcium in the underground waters. The isotopic composition of underground waters is characterized with a high separation of even uranium isotopes.

  For conditions of the Eastern European Platform, it has been established that exogenic groundwaters play the dominating role in the formation of kimberlite pipes. That explains the intense alteration in the rocks, which manifests itself frst and foremost as saponitization. Characteristic changes in the chemical and isotopic compositions of underground waters have for the first time been demonstrated in the intensely changed kimberlite rocks. The development can be useful for explorations of kimberlite formations.