The string of "Dutch" blue beads pictured in the jar in the Opper article about the Diakhite jars are more rounded in their faceting - could these be the late-89th/early 19th century "loquis" beads used in the slave trade?

The Heidi beads incorporate a transparent blue as well as the "Dutch" blue layers, and have more casual faceting just on the ends.
The appearance of similar beads not only in Ghana but Diakhite, Senegal and the Netherlands Antilles still seems to be something worth considering with respect to the use of these beads in the slave trade.