Deep in the Myanmar Mogok region, a tiny reddish-orange crystal sat unnoticed. To the untrained eye, it seemed like many other stones—polished by water, overlooked by miners seeking sapphires. But this unassuming gem, later named kyawthuite, is unlike anything else on Earth; or at least, anything else that we know of.

It is the rarest mineral known to science, with only a single specimen ever discovered.

The only sample found thus far, weighing a mere 1.61 carats (0.3 grams), has sparked immense intrigue among scientists and collectors alike. It now sits alone in a museum case in Los Angeles.

A Singular Gem

The kyawthuite crystal was discovered in 2010 by sapphire hunters in the Chaung Gyi Valley, near Mogok, Myanmar. Initially mistaken for an ordinary gem, it was later identified as unique by Dr. Kyaw Thu, a prominent mineralogist. After extensive analysis, the International Mineralogical Association (IMA) officially recognized kyawthuite as a new mineral in 2015. Today, the sole specimen resides in the Natural History Museum of Los Angeles County, where it is safeguarded as a geological treasure.

Kyawthuite is a bismuth-antimony oxide, with the chemical formula Bi₃⁺Sb₅⁺O₄, with traces of tantalum. These elements, though not exceedingly rare individually, formed under unique conditions that scientists are only beginning to understand.

Kyawthuite’s internal structure is just as unusual. It features checkerboard-like sheets of antimony and oxygen, nestled against bismuth atoms. Its density is eight times that of water, so it is much heavier than meets the eye.

Kyawthuite is thought to have originated in pegmatite, an igneous rock formed during the late stages of magma crystallization. Myanmar’s geology, shaped by the collision of the Indian and Asian tectonic plates, provided the intense heat and pressure needed for such rare minerals to form. This cataclysmic event during the Paleocene-Eocene epoch not only created kyawthuite but also endowed the region with a wealth of gemstones, including the deep-red crystals of painite—the world’s second-rarest mineral; a borate mineral containing the rare pairing of zirconium and boron.

Myanmar’s rich mineral deposits come with a sobering backdrop. Decades of political instability, military control, and human rights abuses cast a shadow over its gemstone trade. Mining practices in the region have drawn criticism for unsafe conditions, forced labor, and child exploitation.

The Mogok region of Upper Myanmar has been known for centuries as the “Valley of Rubies” due to the high-quality rubies that are mined there. The area is also known for producing other precious gemstones like spinel, sapphire, chrysolite or peridot, tourmaline, and even rare gemstones.

Despite all gemstone mining being officially illegal in Myanmar following the expiration of the last mining license in 2020, gemstone mining has boomed since the 2021 coup that put a military junta in power. Tens of thousands of informal miners have filled the void left by the end of official mining, and are being exploited by the military as well as non-state armed groups.

These ethical concerns have prompted some to boycott materials sourced from Myanmar, limiting the study and commercialization of its rare minerals.

Perhaps other specimens of kyawthuite are lurking somewhere in Myanmar. But political challenges and the sheer odds of repeating such a geological fluke make another discovery unlikely. For now, the tiny orange gem in Los Angeles may be the first and last of its kind.

This article originally appeared in November 2024 and was updated with new information.