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Meet kyawthuite, an extremely rare mineral from Myanmar known for only one natural crystal documented by science.
In 2015, the International Mineralogical Association officially approved kyawthuite as a new mineral species, after analyses of a crystal found in Mogok, in the Mandalay region of Myanmar. The case draws attention because, to this day, mineralogical literature records only one single known natural specimen of this mineral.
The stone was scientifically described in 2017 by Anthony R. Kampf, George R. Rossman, Chi Ma, and Peter A. Williams, in the article “Kyawthuite, Bi³⁺Sb⁵⁺O₄, a new gem mineral from Mogok, Burma (Myanmar)”. The type specimen was cut as a gem of 1.61 carats, equivalent to about 0.32 grams, and is deposited at the Natural History Museum of Los Angeles County.
Kyawthuite is the ultra-rare mineral from Myanmar known for only one documented natural crystal
Kyawthuite has the chemical formula Bi³⁺Sb⁵⁺O₄, composed of bismuth, antimony, and oxygen. According to Mindat, a mineralogical database maintained by the Hudson Institute of Mineralogy, it is a valid mineral species approved by the IMA and is described as the only approved mineral of the Bi-Sb oxide group.
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The known crystal has an orange-reddish color, adamantine luster, transparency, hardness of 5.5 on the Mohs scale, and a measured density of 8.256 g/cm³. These data help show that the rarity of kyawthuite is not only in appearance but in an unusual chemical and structural combination in nature.
The recorded type locality is in Chaung-gyi-ah-le-ywa, in the Mogok township, Pyin-Oo-Lwin district, Mandalay region, Myanmar. This area is historically famous for rare gems, but even in this exceptional mineralogical context, kyawthuite remains known for only one confirmed occurrence.
The 1.61-carat stone became a world reference because there is no other confirmed specimen
The most impressive fact is that the type material of kyawthuite is described as a single crystal cut into a 1.61-carat gem. In practice, this means that the entire official identification of the mineral species relies on an extremely small physical specimen, preserved in a scientific collection in the United States.
Mindat reports that the type material is deposited in the Department of Mineral Sciences at the Natural History Museum of Los Angeles County, in Los Angeles, under catalog number 65602. This type of record is essential because it allows researchers to confirm the existence, properties, and original description of the species.
Unlike diamonds, rubies, or emeralds, which may be commercially rare but have multiple known deposits, kyawthuite is rare in an extreme mineralogical sense. So far, the consulted database lists only one locality for the mineral, in Myanmar, with no new confirmed natural occurrences.
The rare mineral was found in alluvium and may have originated from pegmatite
The geological origin of kyawthuite also adds to the mystery. The mineralogical record states that the crystal was found as rolled material in alluvium, that is, in sediments transported by water, and probably originated from a pegmatite.
This detail is important because the original formation environment may not be exactly the same place where the stone was collected. In alluvial deposits, minerals can be carried by natural processes, making it difficult to precisely identify the parent rock and the conditions that produced the crystal.
Pegmatites are rocks known for concentrating uncommon elements and forming rare crystals in the final stages of magmatic crystallization. In the case of kyawthuite, this possible origin helps explain why elements like bismuth and antimony may have combined into such a specific mineral structure.
The composition with bismuth and antimony makes kyawthuite an exception in mineralogy
Kyawthuite belongs to the class of oxides and has a monoclinic crystalline structure. Mindat describes unit cell parameters, monoclinic crystal system, and structural relation with minerals like clinocervantite, but highlights that it is not a direct analogue of other minerals involving bismuth, tantalum, or niobium.
This technical point is central: a mineral is not defined only by the elements it contains, but by the way these atoms are organized. Two materials can have a similar composition and still be different minerals if the crystalline structure is distinct.
In the case of kyawthuite, researchers identified a specific configuration involving Sb⁵⁺O₆ octahedra and Bi³⁺ ions. This atomic organization helped confirm that the crystal was not just a variation of an already known mineral, but a distinct mineral species.
Mogok, in Myanmar, is one of the most famous regions on the planet for gems and rare minerals
Mogok has appeared for decades on the world map of gems because of rubies, sapphires, spinels, and uncommon minerals. The discovery of kyawthuite reinforced the region’s reputation as a natural laboratory of rare and highly selective geological processes.
The type locality of kyawthuite itself is in the Mandalay region, within the Mogok gemological belt. The presence of rare minerals in this area is linked to a complex geological history, involving metamorphism, carbonate rocks, pegmatites, and the circulation of fluids rich in unusual chemical elements.
Even so, kyawthuite stands out because it has not become a “rare gem” with various commercial occurrences. It remains a practically unique scientific mineral, known for a documented specimen preserved in a museum.
Why kyawthuite may be rarer than famous gemstones
The rarity of a gemstone is usually measured by market availability, gemological quality, color, purity, and demand. However, the rarity of a mineral involves another criterion: how many natural occurrences have been confirmed, how many samples exist, and whether the species appears repeatedly in the Earth’s crust.
By this criterion, kyawthuite occupies an extreme position. A blue diamond may be very valuable, but diamonds exist in many mines around the world. Kyawthuite, on the other hand, has only one recognized natural sample in the consulted mineralogical databases.
This does not automatically mean it is the most expensive stone in the world. Commercial value and scientific rarity are different concepts. What makes kyawthuite extraordinary is the combination of unique occurrence, unusual composition, official confirmation, and preservation as a type material.
The small crystal shows how the Earth still holds practically unknown minerals
The existence of kyawthuite shows that the Earth’s crust may still hide minerals whose formation depends on extremely specific chemical conditions. Some emerge only when rare elements, pressure, temperature, fluids, and geological time combine in a way that is difficult to replicate.
Mindat is one of the largest open databases of minerals, localities, and mineralogical occurrences in the world, gathering data used by researchers, collectors, and institutions. Even so, the database itself records kyawthuite with only one listed locality, reinforcing its exceptional status.
The case also helps separate fact from exaggeration: it is safe to say that kyawthuite is among the rarest minerals ever recognized by science. Claiming it is “the rarest in the world” depends on the criterion used, but the existence of only one known natural specimen places this crystal from Myanmar in an almost unparalleled category.
Kyawthuite shows that, even on a planet studied by satellites, laboratories, and global mineral banks, a 0.3-gram stone can still reveal a geological rarity capable of challenging the very notion of mineral abundance.
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