This unusual pendant is based on a genus of diatom called Planothidium. Diatoms are unicellular photosynthetic plankton that make complex shells out of silica. The shell of Planothidium identifies it as a pennate diatom because its shell is bilaterally symmetrical instead of radially symmetrical. Diatoms are found in both marine and freshwater environments and can form algal blooms under ideal conditions of nutrients and light. They are a critical component of aquatic food chains, serving as food for zooplankton and other small animals.