There exists a mineral so rare that only a single specimen has ever been found. This gemstone is called kyawthuite (pronounced cha-too-ite), a small, light brown mineral fragment weighing just 0.33 grams (1.61 carats).
At first glance, one might mistake it for amber or topaz. However, this unassuming piece of stone holds immense and incomparable value.
Kyawthuite was discovered in 2010 by gemologist Kyaw Thu at the Chaung-gyi market in Myanmar. Initially, he believed it to be a mineral known as scheelite. However, after cutting and polishing the gem, he realized he had come across something entirely unique.
Unable to match it with any known minerals, Kyaw Thu sent the stone to the Gemological Institute of America (GIA) laboratory in Bangkok, Thailand. There, mineralogists associated it with synthetic BiSbO4 (bismuth antimonate), though its natural chemical formula, Bi³+Sb⁵+O₄, had never been observed in nature before.
“This is the first one in the world. No other countries have found it,” Kyaw Thu told The Myanmar Times in 2016.
Through Kyaw's fieldwork and purchasing gemstones at the Khanae market, he felt there was something unusual about this stone, so he bought it. Upon returning to Yangon, Kyaw examined it and confirmed that it was unlike any gemstone we had encountered before.
Little is known about the stone itself. It features a vivid orange hue with reddish undertones and white streaks, which appear as powder when the stone is scratched against a rough surface. It also contains hollow tubular inclusions called "healed fractures," which form due to shear stress, providing evidence of its natural origin.
Geologists suggest that kyawthuite may have formed in igneous rock, specifically granite, a type of volcanic rock common in the region where the mineral was found. Much like a fruitcake with various components mixed together, granite often harbors large gem crystals.
The traces of titanium, niobium, tungsten, and uranium found in kyawthuite align with the characteristics of granite formation. Laboratory studies have shown that bismuth antimonate crystals form at high temperatures consistent with cooling magma. Given its apparent rarity, there might be additional unique formation conditions that remain unknown.
Currently, the value of kyawthuite is considered priceless. To put it into perspective, the world’s second rarest gemstone, painite, is valued at $50,000 to $60,000 per carat.
Today, the only known specimen of kyawthuite is safely housed at the Natural History Museum of Los Angeles County.
