Scientists Recreate Golden Sea Silk, the Legandary Thread Once Fit for Emperors

They used farmed Korean shells instead.

Sea silk has one of fashion’s strangest origin stories. It starts as a mollusk’s anchor thread and ends up looking like spun gold. This thread (technically called byssus) is what mollusks use to fasten themselves to rocks, seagrass, or the seafloor.

For centuries, artisans turned those threads into one of the rarest fabrics in the world. Roman elites loved it, as did many popes and emperors. Nowadays, collectors still chase the few surviving examples, paying ungodly amounts of money for them. But the animal that produced the most famous form of sea silk, the Mediterranean noble pen shell, is now protected after steep population declines.

Now, researchers in South Korea say they have recreated a version of the ancient textile using farmed pen shells. Even better, they think they have solved the mystery behind its lasting golden shine. The secret, turns out, isn’t color: it’s structure.

An Imperial Past

Byssus is the mollusk’s built-in tethering system. Some bivalves, including mussels and pen shells, secrete liquid proteins from a gland near the foot. When these proteins hit seawater, they harden into tough, flexible threads that act like natural mooring lines, holding the animal in place against waves and currents.

Humans, crafty bunch that we are, eventually looked at those golden anchor threads and thought: we can use that.

The most famous source was Pinna nobilis, a large Mediterranean clam. This “sea silk” was light, durable, and had a stunning, iridiscent color. It almost looked like gold, and the color didn’t fade away. Artisans would take the byssus, clean and comb it, and spin it into a shimmering golden textile. This material was so cherished it became a symbol of power and prestige, associated with emperors and the elites. It was even used for legendary artifacts like the Holy Face of Manoppello.

But the animal that made traditional sea silk is now protected. Pollution and ecological decline have pushed Pinna nobilis toward extinction, and the European Union bans its harvesting.

So scientists looked for another way.

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A New Source

The team, led by Professor Dong Soo Hwang of POSTECH and Professor Jimin Choi of the Environmental Research Institute, looked to Atrina pectinata, a pen shell cultivated for food in Korean coastal waters.

Like Pinna nobilis, Atrina pectinata produces byssus threads to anchor itself in place. The researchers found that these threads closely resemble traditional sea silk fibers in both structure and chemistry.

Using established processing methods, they turned the Korean pen shell byssus into a golden fiber similar to ancient sea silk. The result is not just a historical reconstruction. It is also a possible way to make use of a material that is usually discarded.

Pen shells are already cultivated for food. Their byssus threads, however, often become waste. If those fibers can be collected and processed, they could become a high-value textile without relying on an endangered Mediterranean species.

This doesn’t mean the material is easy or simple to make. It’s still labor-intensive and tied to a specialized shellfish industry. But it does offer a more sustainable path for reviving a fabric that had nearly vanished.

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It also has some intriguing biological insights.

The Secret Is Structure, Not Dye

The team was curious to see how this type of silk maintains its color for so long. Turns out, it’s structural coloration.

Color comes from two very different processes. Pigment color comes from molecules that absorb some wavelengths of light and reflect others, like dye in a shirt or melanin in hair. Structural color comes from tiny physical structures that bend, scatter, or reflect light in precise ways, producing bright colors without pigments. That’s why soap bubbles, peacock feathers, butterfly wings, and sea silk can shimmer so intensely — the color is built into the material’s microscopic architecture.

This structural color is owed to spherical protein structures called “photonin” inside the fiber. These proteins form layered arrangements that reflect and manipulate light, producing the textile’s golden shimmer.

Because the color comes from structure rather than dye, it resists fading. A pigment can break down under sunlight or wash away over time. A built-in optical structure can continue producing color for far longer.

The study also found that order makes the color stronger. The more neatly the proteins are arranged, the more vivid the golden shine becomes.

Inside the fiber, the proteins are arranged in repeating layers, from tiny clusters to larger structures. Sugar molecules help hold those layers together, giving the thread both its strength and its lasting color. Researchers say this could be used for different types of materials, to ensure they don’t lose color.

“Structurally colored textiles are inherently resistant to fading. Our technology enables long-lasting color without the use of dyes or metals, opening new possibilities for sustainable fashion and advanced materials,” Professor Dong Soo Hwang said in a statement.

The study was published in the journal Advanced Materials.