The World’s Rarest Mineral Is So Uncommon It Has Only Been Discovered Once

A mineral so rare that only one specimen has ever been found in the world exists: kyawthuite (cha-too-ite). This tiny, tawny-hued grain weighs just a third of a gram (1.61 carats), and at first glance, it might resemble amber or topaz. However, its value goes far beyond its appearance.

In 2010, gemologist Kyaw Thu purchased the raw gem at a market in Chaung-gyi, Myanmar, initially mistaking it for scheelite. After faceting the stone, he realized it was unlike anything he had ever seen before. Unable to identify the mineral, Thu sent it to the Gemological Institute of America (GIA) Laboratory in Bangkok, Thailand, where experts linked it to synthetic BiSbO4 – bismuth antimonate – but with a unique formula (Bi3+Sb5+O4), never before found in nature.

“This is the first in the world. It is not found in other countries,” Thu told The Myanmar Times in 2016. “I could tell this stone was unusual and bought it. Upon examination, I realized it was unlike any gem we’d ever found.”

The mineral has a rich orange color with a red overtone and a white streak, leaving behind a powder when rubbed. Its hollow, tube-shaped inclusions, known as en echelon veins, indicate natural formation under shear stress.

Kyawthuite’s Igneous Origin: Formation in Pegmatite and Unique Conditions

Geologists believe kyawthuite is igneous in origin, likely forming within a type of volcanic rock called pegmatite, common in the area where the gem was found. Pegmatite, like granite, contains a mix of minerals and is known for producing large crystals.

Traces of titanium, niobium, tungsten, and uranium in kyawthuite further support this theory. Lab tests show that bismuth antimonite forms at high temperatures similar to those found in cooling magma, suggesting unique conditions for kyawthuite’s formation.

Currently, kyawthuite is considered priceless. For comparison, the second-rarest gem, painite, is valued at US$50,000 to $60,000 per carat.

The only known kyawthuite specimen is securely housed at the Natural History Museum of Los Angeles County.

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