Elemental characterization of some Nigerian gemstones: tourmaline, fluorite and topaz by instrumental neutron activation analysis

Abstract

Instrumental neutron activation analysis (INAA) was employed in the determination of the major and trace element constituents in tourmaline, fluorite and topaz collected from the gemstone mineralization within a SW–NE trending pegmatite zone, central Nigeria. Cost, turnaround time, high sensitivity for certain elements, the non-destructive nature of analysis and its precision and accuracy have combined to make INAA an indispensable method for multi-element determination in virtually all geological matrices. The major element constituents in tourmaline were Al (119,800 ppm), Mn (4,348 ppm), Na (15,540 ppm) and Fe (34,290 ppm). For fluorite, Ca was the major element with a concentration of 552,000 ppm. In topaz, Al was the major constituent with a concentration of 322,800 ppm. The data suites reveal the presence of As, Br, La, Sc, Co, Hf, Ta and Sb in tourmaline, Na, As, Br, La, Yb, Co, Zn, Eu, Hf, Th in fluorite and Mg, Mn, Na, Br, La, Sc, Co and Ta as trace contaminants. No attempt was made to identify the molecular structure of the gemstones as oxygen, fluorine and silicon contents in any of them were not determined.