Analog Of Ewingite, Earth’s Most Complex Mineral, Synthesized

By Michael Horton •  Updated: 11/22/22 •  3 min read

The most structurally complex mineral on Earth, ewingite, has been successfully synthesized in a lab by a group of researchers led by crystallographers from St. Petersburg University.

Ewingite is a mineral discovered in the abandoned Plavno uranium mine in Jáchymov, the Czech Republic, in the mid-2010s. It is the most complicated mineral known to exist on the planet.

Also, the mineral is thought to be very rare because it can only form in very specific thermodynamic conditions.

Ewingite Nanoclusters Of Uranium And Carbonate

synthetic ewingite comparison

Arrangement of supertetrahedral nanoclusters in the structures of Synthetic Ewingite (a) and ewingite (b), which is similar to the body-centered cubic (α-Fe type) packing (c). Interstitial ions and molecules are omitted for clarity; central nanocluster in the body-centered cubic packing is green-colored. Legend: U-centered polyhedra = yellow; red = O atoms; grey = C atoms. Credit: Materials (2022). DOI: 10.3390/ma15196643

Researchers used a combination of low-temperature hydrothermal synthesis and evaporation at room temperature to make a copy of natural ewingite with the same chemical make-up and crystal structure.

According to the researchers, the stability of the discovered mineral is slightly higher than that of the synthetic compound, visual observations and experimental studies show. On the other hand, the synthetic phase can be thought of as a primary, metastable reaction product that re-crystallizes into a more stable form when exposed to the environment.

The crystal structure of ewingite is unique in that it is made up of nanoclusters of uranium atoms and carbonate groups, says principal investigator Vladislav Gurzhiy. He is an Associate Professor in the Department of Crystallography at St Petersburg University.

Practical As Well As Scientific Interest

Before the mineral was found, such structural complexes had never been seen in nature or in man-made compounds. As a result, scientists at St Petersburg University wanted to recreate this one-of-a-kind natural creation in the laboratory.

“Our team has quite a lot of experience in obtaining mineral analogs in the laboratory and synthesizing new compounds with mineral-like structures. However, even with this experience, we worked on the experiment for almost a year and a half. This is how long it took to establish a synthesis protocol to produce large enough crystals to make it possible to obtain a reliable structural model,”

Gurzhiy said.

The composition of the laboratory-created compound differs slightly from that of its natural counterpart.

In the mineral’s structure, the uranyl carbonate clusters are held together by magnesium and calcium atoms, whereas the synthetic compound only contains calcium. However, this has no effect on the crystal structure’s nanocluster packing principle.

This study is not only of fundamental scientific interest, but it is also quite practical because even in depleted deposits like the Plavno mine, a significant amount of uranium remains in scattered form. Understanding the mechanism of secondary mineral formation (recrystallization), which results in the formation of ewingite, will allow control of uranium removal processes into the environment.

“Or, on the contrary, this will make it possible to create conditions under which, if necessary, it will be possible to convert uranium into a dissolved form so that it becomes less dangerous to humans,”

added Vladislav Gurzhiy.

Reference: Tyumentseva OS, Kornyakov IV, Kasatkin AV, Plášil J, Krzhizhanovskaya MG, Krivovichev SV, Burns PC, Gurzhiy VV. One of Nature’s Puzzles Is Assembled: Analog of the Earth’s Most Complex Mineral, Ewingite, Synthesized in a Laboratory. Materials. 2022; 15(19):6643.