Many analyses of the New Caledonian ore - garnierite - have been reported. The composition is Usually taken to lie between the following limits:
| NiO | SiO2 | Fe2O3 | Al2O3 | HgO | H2O | | Garnierite % | 9 to 17 | 41 to 46 | 5 to 14 | 1 to 7 | 6 to 9 | 8 to 16 |
For a time, the ore was reduced with suitable fluxes - fluorspar, cryolite, soda, manganese ore - and powdered coal or coke, in a blast-furnace, and the resulting ferro-nickel obtained approximated:
| Ni | Te | Si | S | C | | Ferro-nickel. | 68.20 | 27.82 | 1.62 | 1.02 | 2.50 per cent |
The process was not satisfactory. It was found better to smelt the ore in a blastfurnace with sulphur so as to form a regulus or matte. The sulphur was added in the form of alkali waste (calcium sulphite), or as gypsum, or iron pyrites. Suitable fluxes are added to form a slag. The mixture is briquetted and smelted. The resulting regulus or matte contains up to 50 per cent, of nickel. The regulus is then enriched either by roasting and melting, or in a converter as in the case of the mattes from the sulphide ores. The enriched matte is then roasted for oxide and reduced. The ore contains no copper, so that the resulting nickel oxide can be directly reduced to nickel. The extraction of nickel from garnierite in Brazil was discussed by E. de Oliviera, J. L. Fohlen, A. Guerreiro, M. Ballay, E. Reitler, and H. E. de Aranjo; and from silicate ores, by B. Bogitch, T. Tatebe, and J. Hissink. |