A method used to remove certain impurities from diamond concentrate with a particle size of 0.5 to 1.0 mm. The material, mixed with 10 times its weight of flake caustic soda, is placed in crucibles and put in a furnace where a temperature of 650 degrees C is maintained for 45 min. After furnacing, the material is rinsed to remove the caustic soda and boiled in a glass beaker containing a solution of 1 part hydrochloric acid and 4 parts 1306 water. After further rinsing, the diamond, free from satellites, is dried on a hotplate.