The Paua shell is a treasure found exclusively in the cold coastal waters of New Zealand. People often encounter this mollusk shell in jewelry and art, drawn to its intensely colorful and shifting internal luster. It is celebrated for its striking appearance, deep cultural significance, and the biological mechanisms that create its famous colors.
The Paua Abalone A Biological Profile
The source of this shell is a large marine gastropod mollusk known scientifically as Haliotis iris. This species is the largest of New Zealand’s three abalone types and is commonly called the blackfoot paua. Paua are endemic to New Zealand, inhabiting shallow, cool, rocky reefs, generally at depths less than six meters. The mollusk uses a strong muscular foot to cling firmly to rocks, preventing predators or currents from dislodging it.
The external surface of the shell is rough, dull, and often encrusted with algae, providing effective camouflage. Beneath this exterior lies the brightly colored inner layer. Paua are herbivores, feeding mainly on kelp, seaweed, and various drifting algae, which influences the final color and thickness of the shell’s interior.
The Structure Behind Iridescence
The brilliant, shifting colors of the Paua shell result from structural coloration, not pigment. This phenomenon occurs when light interacts with the material’s physical structure rather than chemical dyes. The inner layer is composed of nacre, or mother-of-pearl, an organic-inorganic composite material secreted by the mollusk’s mantle tissue.
This nacre layer is constructed from microscopic, stacked tiles of calcium carbonate, specifically aragonite. These hexagonal platelets are held together by thin sheets of an elastic protein matrix. In the Paua shell, the mineral tiles are extremely regular, measuring approximately 0.25 to 0.39 micrometers (µm), a thickness comparable to the wavelength of visible light.
Intense iridescence is created as light enters the shell and reflects off the numerous stacked layers. This process causes two optical effects: diffraction and interference. This precise structural arrangement causes the light to separate, displaying intense blues, greens, purples, and pinks that change with the viewing angle.
Cultural Heritage and Modern Craftsmanship
The Paua shell holds a central place in New Zealand’s culture, especially for the Māori people, who consider it a taonga, or treasured possession. Historically, the shell was used as a food source and as a material for creating traditional items. Its resilience and luminosity made it suitable for crafting fishing lures, decorative elements on tools, and a form of currency.
The most recognizable cultural application is its use as reflective eyes in carved wooden figures and ancestral statues. The shell’s iridescent quality was believed to represent the stars or the watchful eyes of ancestors, adding a sense of life and spiritual presence. The changing colors of the shell are also symbolic of transition and change within Māori belief.
The shell is now a key component of modern New Zealand craftsmanship and commerce. Contemporary artisans utilize the vibrant nacre in high-end jewelry, such as earrings, pendants, and rings. It is also frequently used for decorative inlay work in furniture, musical instruments, and ornamental objects, requiring careful grinding and polishing to reveal its full color spectrum.
Protecting the Paua Resource
Due to its cultural and commercial value, the Paua resource is subject to strict conservation management in New Zealand. The government regulates its harvest through the Fisheries Act, employing a system of quotas and size limits to ensure sustainability. This management structure applies to both commercial and recreational gathering.
For the commercially important blackfoot paua, Haliotis iris, a Minimum Legal Size (MLS) of 125 millimeters (mm) is enforced. This size restriction allows the mollusks to reach sexual maturity and reproduce before legal harvest. Recreational fishers are also subject to daily bag limits, which have been reduced in certain areas to protect breeding stocks. Divers are prohibited from removing the meat (shucking) until they are above the high-water mark, allowing officers to verify the shell size.