"Puka" (pronounced pooh-kah) shells are naturally occurring bead-like objects which can be found on some beaches in Hawaii. The beach-worn apex of a cone snail shell, a kind of seashell from a sea snail. Tumbled in the surf over long periods of time they are worn down until all that is left is the tip of the shell with a hole in the middle.

"Puka" is the Hawaiian word for hole and refers to the naturally occurring hole in the middle of these rounded and worn shell fragments. These natural beads are made into necklaces.

Real "puka" shells are not flat: one side of the bead is slightly convex; the other is concave. The concave side of the bead clearly shows the spiral form of the interior of the spire of the cone shell.

The original all-natural "puka" shells were very easily made into necklaces, bracelets and anklets because they were naturally pierced, which enabled them to be strung like beads.

"Puka" shell jewelry first became a popular item in Hawaii during the 1960s, as an attractive and inexpensive lei that could be made and sold on the beach. In the 1970s, this type of shell jewelry became highly sought after, and prices skyrocketed.

More Info: en.wikipedia.org