The humic-mineral agent from naturally occurring carbon-series humites and caustobioliths comprises humic acids and salts thereof, naturally hydrated humic acids, hydrolyzed humic acids, hydrated and hydrolyzed humic-mineral and mineral complexes of parent carbon-series humites and caustobioliths chemically bound to the naturally hydrated humic acids. The method for preparing a humic-mineral agent comprises crushing and disintegrating of carbon-series humites and caustobioliths and mixing them with an alkali. The carbon-series humites and caustobioliths are crushed and disintegrated when their moisture content is close to the natural level at which humic acids are in a naturally hydrated state, hot water is added to the. Next an alkali is added thereto and the mixture is hydrolyzed till obtaining the end product having consistency from viscous-flow to plastic and the pH value of from 6.5 to 8. The method for detoxication of polluted soil. The method for detoxication of waste products of mining and processing useful minerals and for reclaiming waste piles and tailing pits, the method for sewage water treatment and the method for salvaging sewage sediment are carried into effect by using the humic-mineral agent mentioned before.