Sulfidation of minerals

Claim 1

THE PROCESS OF SULFIDING SOLID MINERAL MATERIAL CONTAINING COMPONENTS REACTIVE TO FORM METALLIC SULFIDES, WHICH COMPRISES INITIALLY HEATING SUCH A MINERAL MATERIAL BY CONTACT WITH COMPARATIVELY LARGE VOLUMES OF A TREATING GAS INTRODUCED INTO A PRIMARY TREATING ZONE, SAID GAS BEING COMPOSED OF A PREHEATED ESSENTIALLY INERT CARRIER GAS CONTAINING GASEOUS SULFIDE IN DILUTE CONCENTRATION THEREIN, MAINTAINING CONTACT BETWEEN SAID MINERAL MATERIAL AND SAID TREATING GAS IN SAID PRIMARY TREATING ZONE FOR A PERIOD AT LEAST SUFFICIENT TO HEAT SAID MINERAL MATERIAL TO DESIRED REACTION TEMPERATURE AND SIMULTANEOUSLY EFFECTING THEREBY THE INITIAL SULFIDATION OF SAID REACTIVE COMPONENTS, AND THEREAFTER CONTACTING THE THUS HEATED MATERIAL WITH A COMPARATIVELY SMALL VOLUME OF CONCENTRATED SULFIDING GAS FOR A CONTROLLED PERIOD IN A SUBSEQUENT TREATING ZONE BY INTRODUCTION OF SAID CONCENTRATED SULFIDING GAS INTO AND SUBSEQUENT TREATING ZONE UNDER INDEPENDENTLY CONTROLLED CONDITIONS AND AT A TEMPERATURE LOWER THAN THAT OF THE MINERAL MATERIAL INTRODUCED IN SAID SUBSEQUENT ZONE THEREBY