8mm Red Round Sea Shell Pearl Necklace 18in Brand New Without Tags Red Sea Shell Pearl Pearl Size: 7.5 - 8.5mm Alloy Clasp Color may be lighter or darker due to different PC/Cell phone screens Shell Pearls are made from the inner lining of oyster shells, also known as Mother of Pearl. The substance is ground to a fine powder, shaped, dyed and coated with natural pearl nacre and then a protective coating to give it luster. The shell pearl is a pearl made in the laboratory with natural materials but it is an imitation pearl.