These are strands of small polished paua shells.
There are typically 7 shells per strand. These strands have shells that are 1.5" to 2" long by 1" to 1.5" wide. Four weighed 1.7 ounces or 50 grams. The shells are finished on both sides and the holes are small and nicely drilled.
Paua is the species of abalone shell (Haliotis iris) found only in the cold waters of southern New Zealand. The coloring varies from shell to shell and has an amazing iridescence. The lighting in the photos above does not do justice to the array of colors found in these shells. The government of New Zealand strictly controls the harvesting of abalone for food. The shells are a natural by-product.