Also known as mother-of pearl, nacre is a composite material produced by some mollusks as an inner shell layer. It is also the material of which pearls are composed. Nacre appears iridescent because the thickness of its layers is close to the wavelength of visible light. These structures interfere with different wavelengths of light at different viewing angles, creating structural colors.

While visiting the Monterey aquarium we experienced a touch pool that housed abalone. These single shell mollusks are prized for both their meat and shells. Native Americans would leave huge mitten piles of shells ashore. The pictured buckle is an example of the variety of jewelry that has been fashioned from their shell. These twin wants have led to a decline in the abalone population, resulting in much smaller sized creatures than previously found. I remember eating abalone, before that was banned and our house used empty shells as soap dishes. A solution to this problem now is the commercial farming of these creatures.