Iridescence of a shell of mollusk Haliotis Glabra

Abstract

Pearls and shells of some mollusks are attractive inorganic materials primarily owing to the beauty of their natural lustrous and iridescent surface. The iridescent colors can be explained by diffraction or interference or both, depending on the microstructure of the surface. Strong iridescent colors are very evident on the polished shell of the mollusk Haliotis Glabra, commonly known as abalone. It would be interesting to study how these colors are produced on the surface of the shell. By using a scanning electron microscope (SEM), the surface of the shell is found to have a fine-scale diffraction grating structure, and stacks of thin crystalline nacreous layers or platelets are found below the surface. These observations suggest that the iridescent colors are caused by both diffraction and interference. From measurements done on the diffraction patterns that were obtained using a He-Ne laser illuminating the shell, the groove width of the grating structure was derived. Good agreement was found between the derived groove density by diffraction and that measured directly using the SEM. The crystalline structure of the nacreous layers of the shell is studied using Fourier transform infrared spectroscopy and SEM observations. The infrared absorption peaks of 700, 713, 862 and 1083 cm-1 confirmed that the nacre of the shell is basically aragonite. The strong iridescent colors of the shell are the result of high groove density on the surface which causes diffraction. The uniform stacking of layers of nacre below the surface of the shell also causes interference effects that contribute to the iridescent colors.

Gastropod nacre: Structure, properties and growth — Biological, chemical and physical basics

“…[72,73]) report similar groove structures on polished shell surfaces of Pinctada margaritifera and Haliotis glabra (Fig. 8) respectively.…”

Hybridized/coupled multiple resonances in nacre

“…[26][27][28] From an optical standpoint, nacre has been studied to better understand the unique colors in terms of diffraction from fine-scale grating structures on the shell surface and interference from the inner nacreous layers. [29][30][31] In particular, photonic band states, which imply perfect ordered nanostructures, are speculated to play an important role in the distinct colors of abalone shells and pearls. 32,33 However, these unique nanostructures of nacre have not yet been exploited as optical resonators.…”

Replication of Papilio maackii Ménétriés butterfly scale structural color using a magnetron sputtering method

“…Many artifices are employed by creatures to display metallic-like colors as signals, defending against predators, and camouflage [1][2][3]. Mäthger et al [4] studied the Paradise whiptail (Pentapodus paradiseus) and found that it has distinct reflective stripes on its head and body.…”