Kyawthuite: The World's Rarest Mineral in a Single 1.6-Carat Specimen.

Kyawthuite is the rarest mineral on Earth, known from only one sample found in Myanmar. Its chemical formula is Bi3+Sb5+O4, with traces of tantalum. The transparent reddish-orange stone is composed of checkerboard sheets of octahedra Sb5+O6 parallel to Bi3+ atoms. It is named after Dr. Kyaw Thu, a former geologist at Yangon University. A synthetic replica of kyawthuite exists, so there's no need to steal the only sample on Earth from its home at the Natural History Museum of Los Angeles County.