Cf. Garrard, T., Gold of Africa, Geneva, 1989, p.24, fig.14. The author describes the technique in which tiny granules of gold are applied to the large bead to produce a shimmering effect. The ornaments are found principally in Mali and Senegal, where they are highly prized. The form can be traced back at least a thousand years in the Middle East and was probably introduced to West Africa through trans-Saharan trade.