Materials: 16 inch necklaces are typically made from natural seashells, specifically the fragments or "chips" of various shells, such as clam or cone shells. The white color is natural, though the exact shade may vary from bright white to cream or light brown.
Design: The beads have an irregular, tumbled shape, mimicking the natural wear of shells found on the beach. The size of the shells often graduates, starting smaller near the clasp and getting larger towards the front of the necklace. The one in the image also includes small, dark (likely black or hematite) accent beads.
