Dynamic strategies of beadwork communication used in and across cultures are traceable. This is most clearly seen in Zulu beadwork used to convey messages to lovers as an important form of marriage negotiation. By the nineteenth century, this form of negotiation had developed into a highly sophisticated courtly art. The beaded panels, commonly known today as “love letters,” were originally composed of geometric abstract shapes in various configurations, but by the mid-twentieth century, this wholly visual system gave way to using written text. In many types of beadwork, it is the material used to produce beads that conveys meaning. This is seen in a Somali amber Porte Koran necklace in the exhibition that has beads made of amber and agate, both regarded as powerful medicines for healing and preventing maladies.
Information above from here.
Another site about this type of beadwork here.