10 Things So Rare They’ve Only Been Found Once

Some discoveries are the first—and likely the only one—of their kind. But uniqueness is not their only trick. Extreme rarity often begets mystery, as human knowledge has nothing to compare these oddities against. Such cases make for fascinating reading, too. From an impossible stellar explosion to a glass brain, here are ten things you will probably never encounter in real life.

Related: 10 Exceptionally Rare Oddities Found on Islands

10 Kyawthuite

The rarest mineral on Earth is an orange beauty called kyawthuite. It was accidentally discovered in 2010 when a geologist browsing a gem market in Myanmar picked up a small unworked crystal he assumed was scheelite. Once cut and polished, however, the stone’s identity was clearly wrong. Unable to match it to any known mineral, he sent it to the Gemological Institute of America for analysis.

Mineralogists there identified the crystal as the natural form of bismuth antimonate—previously known only as a synthetic compound. Formally recognized in 2015 by the International Mineralogical Association, kyawthuite remains the only known specimen ever found. Weighing just one-third of a gram, it likely formed under extremely specific volcanic conditions that scientists still cannot replicate or fully explain.

The lone fragment now sits securely in the GIA’s collection, listed simply as “priceless,” which feels appropriate for a mineral the Earth may never create again.^[1]

9 A Yellow Penguin

Most penguins share the same iconic black-and-white tuxedo look. But in 2019, wildlife photographer Yves Adams captured something that stunned the scientific community—a king penguin glowing bright, lemon yellow. Its normally black back and flippers were white, while its head, chest, and throat were an almost surreal golden-yellow, making it look like a misplaced tropical bird bobbing off South Georgia Island.

Experts believe the color shift came from leucism, a condition in which animals lack melanin in some or all of their feathers. In king penguins, that missing pigment can turn normally dark plumage a vivid yellow. Leucistic penguins are incredibly rare, with estimates suggesting fewer than one in tens of thousands. Others have suggested a form of albinism, though the presence of pigment in some areas makes leucism more likely.

Whatever the cause, the bird remains the world’s only documented yellow king penguin—a lone burst of color in a monochrome species.^[2]

8 An Intersex Whale

In 1989, researchers collected skin samples from southern right whales using specialized biopsy crossbows. The samples sat in storage for decades, forgotten—until thirty-six years later, when scientists at Saint Mary’s University in Canada examined them and found something extraordinary.

One sample, labeled Eau10b, initially appeared to be genetically female, with two X chromosomes. But deeper sequencing revealed something unexpected: the whale also carried the SRY gene, typically found only on the Y chromosome. Further testing confirmed an XXY genetic arrangement, making Eau10b the first and only intersex southern right whale ever identified.

Because whales spend much of their lives in the deep ocean and because sex chromosome anomalies don’t always produce visible traits, the odds of ever identifying another case are extremely low. This lone genetic oddity may be the only confirmed intersex whale science will ever see.^[3]

7 Large Carnivore Pollinators

Pollinators typically come in small packages—bees, butterflies, hummingbirds. Certainly nothing the size of a fox, let alone a wolf. But in 2024, researchers recorded a natural behavior never before seen: Ethiopia’s endangered wolves drinking nectar and pollinating flowers as they did so.

Camera traps revealed the wolves visiting the tall, torch-shaped blooms of the Ethiopian red hot poker plant. As the wolves dipped their muzzles inside for nectar, pollen dusted their faces and transferred to the next flower they visited. A single wolf could hit 30 blossoms on a nectar run, making them surprisingly effective pollinators.

This discovery marks the only known case of a large carnivore not only hunting prey but also routinely consuming nectar in the wild. It also highlights how little we truly know about rare or endangered species—and how many unusual ecological relationships may still be hidden in remote corners of the world.^[4]

6 Hein’s Stingray

In 1902, the Austrian couple Wilhelm and Marie Hein were placed under house arrest by a local sheikh while living in the seaside town of Qishn, Yemen. With little else to do, Marie collected more than 2,000 biological specimens—including two tiny stingrays she preserved in a jar of formalin. The jar was sent back to Austria, where it sat untouched for more than a century.

In 2017, biologist Alec Moore tracked down the jar in the Natural History Museum in Vienna and examined the stingrays in detail. He measured their fins, snout angle, gill structure, and body proportions, eventually confirming what he suspected: they were an unknown species. In 2018, the fish were formally named Hemitrygon yemenensis, or Hein’s Stingray.

Because the species is believed to inhabit waters off war-torn Yemen—an area currently inaccessible to researchers—the two specimens Marie Hein collected may be the only ones humanity will ever see. Some scientists fear the species may already be extinct.^[5]

5 A Four-Star System

In 2025, a team of Chinese astronomers searching for brown dwarfs—small, faint “failed stars”—stumbled onto something unprecedented. They discovered a quadruple star system unlike any other known in the Milky Way, consisting of two brown dwarfs orbiting each other while jointly orbiting a pair of red dwarf stars.

Because all four stars were born from the same material at the same time, the find provided a rare benchmark for studying stellar evolution. Brown dwarfs cool continuously over their lifetimes, making them notoriously difficult to date. But by analyzing the more cooperative red dwarfs, astronomers could finally estimate the age and composition of their elusive brown dwarf companions.

The system, located roughly 300 light-years away, is between 300 million and 2 billion years old. Brown dwarfs are Jupiter-sized but can have up to 30 times Jupiter’s mass, with temperatures reaching about 1,016°F (547°C). No other four-star configuration like it has ever been found.^[6]

4 A Skinless Shark

In 2019, marine scientists trawling off Sardinia pulled up a blackmouth catshark that shouldn’t have been alive. The shark had no skin. Instead of the spotted pattern typical for its species, its body was smooth, raw-pink, and completely exposed—a condition that should have been fatal.

Examination revealed the shark lacked the external skin layers, much of the dermis, all dermal denticles (the tooth-like scales that protect sharks), and all functional teeth. Yet the animal appeared healthy. Fortunately for this shark, its species swallows prey whole, which allowed it to survive despite its lack of teeth.

The cause of the condition remains unknown. It may have resulted from a developmental anomaly during embryonic growth, or from long-term exposure to pollutants or stressors in the Mediterranean. Despite repeated trawls in the same area, no second skinless shark has ever been found.^[7]

3 The Barbenheimer Star

In 2024, scientists analyzed J0931+0038, a red giant first cataloged in 1999, and realized it should not exist. Its chemical signature pointed to an extraordinary origin: a single massive star up to 80 times the mass of our Sun, nicknamed the “Barbenheimer Star”—a playful reference to the dual 2023 film releases of Barbie and Oppenheimer.

This enormous ancient star exploded as a supernova roughly 13 billion years ago. That explosion produced J0931 from its remnants. But the problem is the chemical makeup of the survivor. J0931 lacks light elements and contains unusually high concentrations of midweight and heavy elements—levels that shouldn’t be possible from a star born so early in the universe. Even stranger, a star the size of Barbenheimer shouldn’t explode outward at all; it should collapse into a black hole.

The discovery challenges current theories of stellar evolution and early-universe nucleosynthesis. In short, Barbenheimer shouldn’t have lived the way it did, shouldn’t have died the way it did, and shouldn’t have created a star like J0931—but it did.^[8]

2 Gwada-Negative

The International Society of Blood Transfusion recognizes 48 blood groups, but in 2025, scientists added a new one—discovered in a single patient in Guadeloupe. Lab technicians noticed that her blood was incompatible with every donor sample tested, even those from her siblings. Further genetic sequencing revealed why.

The patient carried a mutation that removed a specific sugar molecule involved in the structure of her red blood cell membranes. Without it, her blood did not match any known blood group. Researchers named the new type Gwada-Negative, after the island where she lived.

Because no compatible donors exist and because no one knows how her body would react to other blood types, transfusions are too dangerous to attempt. For now, the only possible way to save her life in a medical emergency would be to artificially manufacture Gwada-Negative blood—a technique that may still be years away.^[9]

1 A Glass Brain

When Mount Vesuvius erupted in AD 79, its pyroclastic surge instantly killed victims in Pompeii and nearby Herculaneum. In the 1960s, archaeologists uncovered one such victim—a young man lying face-down in a bed inside the College of the Augustales.

In 2020, researchers reanalyzing the remains discovered something astonishing inside his skull: shiny, black, glass-like fragments. Chemical testing suggested that the extreme heat of the eruption had flash-vitrified the man’s brain tissue—something never before seen in archaeology. A follow-up study in 2025 confirmed that the material contained proteins, neurons, and axons consistent with human brain matter.

Scientists believe the vitrification occurred when a super-heated ash cloud engulfed the building, rapidly heating the brain to extreme temperatures before an equally rapid cooling. Those conditions are almost impossible to replicate naturally, which is why this remains the only known example of a fossilized glass brain in human history.^[10]