During an expedition to Kamchatka, scientists from the Department of Crystallography at St Petersburg University discovered three unique minerals. Due to their properties, they will be in demand in various areas of the high-tech industry: from microelectronics to the development of quantum computers. The finds were named after the indigenous peoples of the Kamchatka Peninsula: itelmenite, koryakite, and aleutite. The latest research findings have been published in the scientific journal Mineralogical Magazine.
For the last six years, a research team supervised by St Petersburg University Professor Oleg Siidra has been studying the fumaroles of Tolbachik Volcano – relatively small fissures through which hot vapours and gases emitted from magma escape. Such geological features are distinguished by their rich mineralogical diversity. After each expedition, the scientists return with field data, the study of which leads to amazing discoveries. Three new minerals were no exception – their crystal structure and properties do not even have close analogues among synthetic compounds or known groups of mineral species. So, itelmenite and koryakite contain a sulfate anion, and aleutite contains two negatively charged ions simultaneously – the arsenate ion and the vanadate ion.
The complex vanadate-arsenate aleutite contains 13 chemical elements simultaneously. In its structure, unusual complexes with copper form fragments derived from Kagome nets. Oleg Siidra is a St Petersburg University professor and the head of the research team. He notes that such structural elements demonstrate very interesting magnetic properties. The research team has already demonstrated this using dokuchaevite – the mineral discovered recently by the scientists.
‘Additionally, aleutite belongs to a very interesting class of substances common among synthetic compounds, but rare for minerals: salt-inclusion solids. In the wide channels of aleutite, there is a significant range of elements in the form of electroneutral chloride complexes with monovalent copper, potassium, lead, rubidium, and caesium. The established crystal structure shows that aleutite, due to the formation of frustrated complexes with copper, should exhibit the properties of a spin quantum liquid. In theory, the use of such magnetic properties will help to create a quantum computer,’ explained Oleg Siidra.
The itelmenite structure is a new type of framework structure made of sulphur, magnesium and copper atoms. There is a striking similarity between the architecture of the crystal structure of the mineral and the traditional patterns on the clothes of the Itelmens. The scientists decided therefore to name the find after the indigenous people of Kamchatka.
‘The framework of the itelmenite structure contains channels that contain sodium atoms. Synthetic compounds with a similar composition and a similar crystal structure are used as Na-ion batteries and rechargeable cells. The development and production of new high-performance batteries is one of the key priorities of modern high-tech industry throughout the world,’ said Oleg Siidra.
Koryakite is named after other inhabitants of the peninsula – the Koryaks – and is unusual not only for minerals. Anhydrous sulphates of transition metals are rare in the mineral world. They are formed almost exclusively on the fumaroles of active volcanoes or in places where natural coal fires occur. The crystal structure of koryakite also belongs to one of the most studied materials of our time – NASICON (abbreviation of Na Super Ionic CONductor) – among which there are very few natural minerals. These compounds are also widely used in the manufacture of batteries and rechargeable cells. More than a hundred NASICONs are known among synthetic materials. However, it is the particular composition of the new mineral that has never been encountered before.
As a result of high-temperature processes and the growth of crystals from gas on the fumaroles, the crystal structure of koryakite is very unusual. On the one hand, it is similar to the structure of a simple anhydrous aluminium sulphate. But in koryakite, part of the aluminium is replaced by magnesium, which made it possible for potassium and sodium ions to enter the channels. It is the latter circumstance that allows us to consider the Kamchatka find as a promising prototype of a material for the industry. For a more detailed analysis of the properties of koryakite, the scientists are now engaged in the synthesis of its pure analogue.
Unusual properties of the finds with potential for use in materials science and industry should be studied using synthesised analogues of natural minerals. So far, crystallographers have managed to synthesise an analogue of itelmenite in the laboratory. This will make it possible for them to study in detail its electrochemical properties. Work on synthesising pure, without impurities, samples of koryakite is still underway using the equipment of the laboratory of the Department of Crystallography. Evgeny Nazarchuk has obtained data on the structures of all three new minerals using the equipment of the Resource Centre for X-Ray Diffraction Studies at the Research Park of St Petersburg University. He is Associate Professor at the Department of Crystallography and a member of the research team supervised by St Petersburg University Professor Oleg Siidra.
‘Our approach is to implement a full cycle: from collecting mineral material in the field to successful synthesis and study of their properties. We follow the strategy “From minerals to materials”, which distinguishes our team from others in Russia and the world. Over the past years, we have succeeded in modelling the processes of mineral formation on volcanoes. We have also managed to obtain analogues of many minerals discovered by our team over the last five years in Kamchatka,’ said Oleg Siidra.
The fieldwork and research by the team have been supported by grants from the Russian Science Foundation (No 16-17-10085) and the Russian Foundation for Basic Research (No 19-05-00413).