Ferrihydrites (FHYDs) with the general formula of FeOOH center dot nH(2)O are naturally occurring oxyhydroxide minerals found in environments varying from river beds, lakes, and marshes to even living organisms. Here, we report the synthesis of a new kind of synthetic doped amorphous two-line FHYDs containing aluminum and copper, which are not usually known to be found in nature. Transmission electron microscopy carried out on synthetic FHYDs showed them to be amorphous in nature with some nanosized groupings in the form of nanoclusters of about 50-200 nm size without any hint of diffraction fringes associated with crystalline order. The synthetic doped FHYDs exhibit unique properties and have been characterized extensively by magnetic measurements, X-ray diffraction, and electron microscopy as well as by Mossbauer spectroscopic studies. After promotion with potassium, these FHYDs were found to have high activity as catalysts for the Fischer-Tropsch (F-T) conversion of syngas to liquid fuels over a period of similar to 100 h in a fixed bed reactor at 265 degrees C and 100 psig pressures. The comparison of the preliminary 100 h data for the synthetic doped FHYD catalyst with those of a commercial fixed-bed catalyst pretreated under similar conditions suggests somewhat better catalytic activity of the synthetic doped FHYD than that of the commercial fixed-bed catalyst. The F T oil and wax obtained as products were characterized extensively using gas chromatography, quantitative C-13 NMR, and distortionless enhancement by polarization transfer NMR