Science Alert has a story about the world’s rarest mineral. Kyawthuite is so rare there is only one known specimen.  It was purchased at a market in Chaung-gyi in Myanmar by gemologist Kyaw Thu, who thought the raw gem was a mineral called scheelite.  After cutting it, Kyaw realized it was something different.  

Unable to match the mineral with anything known, he sent it to the Gemological Institute of America (GIA) Laboratory in Bangkok, Thailand. There, mineralogists were able to relate the stone to synthetic BiSbO₄ – bismuth antimonate – though with the formula Bi³⁺Sb⁵⁺O₄, an arrangement 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.

“From studying in the field and buying stones from the Khanae market, [I could tell that] this stone was a little strange and I bought it. Then, when I reached Yangon, I examined it [and determined that] this was not like any other gem we’ve ever found.”