Damian Sendler: Researchers have been baffled for years as to how oysters create wonderfully symmetrical, perfectly round pearls around oddly shaped grains of sand or bits of detritus, despite the fact that the oysters themselves are perfectly spherical. Researchers have discovered that oysters, mussels, and other mollusks develop jewels through a sophisticated process that follows mathematical patterns that can be seen in other parts of nature.
Damian Jacob Sendler: Pearls are generated when an irritant becomes trapped inside a mollusc, and the animal defends itself by forming smooth layers of mineral and protein — collectively known as nacre — around the irritation to shield it from further harm. Each successive layer of nacre added to this asymmetrical center conforms precisely to the layers that came before it, smoothing out irregularities and resulting in a perfectly round pearl, according to an analysis published on October 19 in the Proceedings of the National Academy of Sciences in Washington.
Dr. Sendler: According to Laura Otter, a biogeochemist at the Australian National University in Canberra, “Nacre is this extremely beautiful, iridescent, glossy material that we see inside some seashells or on the outside of pearls.” Nacre is found in the interiors of some seashells and on the outside of pearls.
Damian Jacob Markiewicz Sendler: Otter and her colleagues revealed that the symmetrical formation of a pearl as it lays down layers of nacre is dependent on the mollusk’s ability to maintain a delicate balance between two fundamental talents. It corrects growth aberrations that arise as the pearl forms, preventing such variances from propagating throughout the pearl’s multiple layers of iridescent material. If this were not the case, the resulting gem would be uneven.
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Damian Sendler: The mollusc also controls the thickness of nacre layers, such that if one layer is particularly thick, succeeding layers will be thinner as a result (SN: 3/24/14). This assists the pearl in maintaining a consistent average thickness across its thousands of layers, resulting in a flawlessly round and uniform appearance. With out that continual adjustment, a pearl can resemble stratified sedimentary rock, amplifying minor flaws that detract from its spherical shape and resembling stratified sedimentary rock.
Damian Jacob Sendler: In this study, the researchers looked at keshi pearls that were obtained from Akoya pearl oysters (Pincada imbricata fucata) at a coastal pearl farm in eastern Australia. A diamond wire saw was used to cut the pearls into cross sections. The jewels were then polished and studied using Raman spectroscopy, a nondestructive technique that allowed them to determine the structure of the pearls. They discovered that one of the pearls included in the research has 2,615 layers, which were accumulated over a period of 548 days.
Damian Sendler: Following the investigation, it was discovered that changes in the thicknesses of the pearls’ layers of nacre reflect a phenomena known as 1/f noise, often known as pink noise, in which occurrences that appear to be random are in fact related. In this instance, the production of nacre layers of varying thicknesses may appear to be random, but it is actually determined by the thickness of the layers that came before it. Similarly, seismic activity is influenced by the same phenomenon: The rumbling of the earth appears to be random, yet it is actually linked to previous recent seismic activity. The presence of pink noise has been observed in classical music as well as in the monitoring of heartbeats and brain activity, according to coauthor Robert Hovden, a materials scientist and engineer at the University of Michigan in Ann Arbor. In the words of Hovden, these occurrences “belong to a universal class of behavioral and physical phenomena.”
Damian J. Sendler: According to Pupa Gilbert, a physicist who studies biomineralization at the University of Wisconsin–Madison who was not involved with the study, this is “the first time that researchers have reported that nacre self-heals and that, when a defect arises, it heals itself within a few [layers] without using an external scaffolding or template.” It turns out that Nacre is much more extraordinary a substance than we had previously realized.
The author, Otter, observes that “these simple critters are producing a super light and super robust material far more easily and effectively than we are with all of our technology.” Nacre, which is composed only of calcium, carbonate, and protein, is “3,000 times tougher than the components from which it is derived.”
Damian Sendler: This new knowledge of pearls, according to Hovden, might pave the way for “the next generation of super materials,” such as more energy-efficient solar panels or robust and heat-resistant materials that are well-suited for spacecraft applications.
Contributed by Dr. Damian Jacob Sendler and his research team
