Ni-sepiolite-falcondoite in garnieriteudmineralization from the FalcondoudNi-laterite deposit, Dominican Republic

摘要

New chemical and structural data on sepiolite-falcondoite in garnierite veins fromudthe Falcondo Ni-laterite deposits, central Dominican Republic, are reported. Samples of Ni-sepiolitefalcondoiteudvary in colour from whitish green to green depending on the NiO content (wt.%) and theudamount of silica present. The texture is normally schistose and friable but samples with considerableudquartz and/or amorphous silica are compact and hard. Back-scattered electron images indicate thatudthe samples are composed of at least three generations of Ni-sepiolite-falcondoite. The extremeudrefined cell parameters for Ni-sepiolite-falcondoite vary from 13.400(2), 27.006(4), 5.273(1) A˚ toud13.340(3), 27.001(6), 5.267(1) A˚ (space group Pncn). As the Ni content increases there is a smalludreduction in the a parameter. Chemical compositions determined by electron probe microanalysisudcover a large interval of the Ni-sepiolite-falcondoite solid solution (Fal3 and Fal77). Individualudsamples show a considerable range in composition with the widest range determined in one sampleudfrom 4.63 to 22.40 wt.% NiO.