Cocoa, (Vegetable Ivory)

Vegetable ivory was a popular material for vintage rosary beads, and is still available, although uncommon.

Also called Coca, Coco, or Tagua, it is not related to the coconut palm. An ivory substitute since at least the mid 19th century, vegetable ivory is beautiful in it's own right. It has a texture and hardness similar to elephant ivory, with a rating of 2.5 on the scale of mineral hardness.

According to legend, a ship sailing from South America to Germany in 1865 carried a load of tagua nuts as ballast. Upon arriving at dockside in Hamburg, curious stevedores began playing with the taguas, and, noticing their ivory-like characteristics, began using it for scrimshaw.[2]
Ivory nuts were a popular material for buttons, beads and small sculptures until the 1950s, when plastics greatly reduced the demand for tagua nuts.

Several tropical palms produce vegetable ivory. Phytelephas aequatorialis, also known as the ivory-nut palm, grows along the banks of tropical American rivers from Panama and Colombia to Peru. Metroxylon amicorum, the Caroline ivory-nut palm, is native to the Caroline Islands of Micronesia. Hyphaene ventricosa is an African palm native to islands and banks of the Zambezi River near Victoria Falls.

  Mother of Pearl

 (2) Anne Underwood, International Wildlife 21, no.4 (July Aug 1991), pg 29.