When they hear the word “Dolomite,” most people think of long hikes, fast ski runs, or daring climbing expeditions. Geologically, the Dolomites mountain range in Italy consists mainly of the rock and mineral dolomite, the formation of which remains unclear to this day. Equally unclear are the significant fluctuations in dolomite formation over the course of millions of years. A new study by Osnabrück University and Aalto University in Finland has now identified a specific spatial arrangement of atoms on the crystal surface as a factor in the formation of dolomite. The study, led by Dr. Philipp Rahe, was recently published in the journal Nano Letters.
“What makes dolomite special is the precisely alternating arrangement of magnesium and calcium ions in the crystal lattice—that is, within the mineral dolomite. How this regulation forms in a controlled manner remains a problem that is not yet fully understood,” explains Dr. Philipp Rahe, head of the Molecular Quantum Structures research group at the School of Physics at Osnabrück University.
While investigating the related carbonate calcite, the Osnabrück physicists came across the crystal structure of dolomite and discovered that the atomic arrangements on two sides of the crystal can only be transformed into one another by reflection. Similar to human hands, these surfaces cannot be transformed into one another by rotation or translation—they exhibit what is known as “chirality.”
Together with Prof. Adam Foster from Aalto University in Finland, the two surfaces were examined using ultra-high-resolution microscopy and state-of-the-art quantum chemical methods, confirming the existence of these chiral surfaces. “Above all, we were able to experimentally rule out the possibility that the surface could be reconstructed, thereby eliminating the chirality,” explains Paul Laubrock, a research associate at Osnabrück University. “We were also able to detect chirality in the first layer of adsorbed water, which has implications for the physical and chemical properties of this surface,” adds Dr. Jonas Heggemann, who conducted the experiments together with Paul Laubrock.
The study shows that chirality is a property of the dolomite surface and should be taken into account as a parameter in the formation of dolomite. “Amino acids and sugars occur on Earth in only one chiral form each. Considering that the formation of minerals in the upper Earth’s crust occurs almost exclusively in contact with a solution that typically contains chiral components of organic cells, it stands to reason that chiral molecules contribute to the formation of dolomite,” explains Dr. Philipp Rahe. “Accordingly, we will next investigate the adsorption of biomolecules onto this surface,” adds Dr. Jonas Heggemann.
Dr. Philipp Rahe’s research group is investigating the interaction of water with mineral surfaces, as well as the formation of molecular structures on these surfaces, in several projects. The research is conducted using ultra-high-resolution atomic force microscopy, which can measure individual atoms. This project was funded by the German Research Foundation (DFG) and the Central Research Pool at Osnabrück University.
The original publication is available online.
Further information for the media:
Dr. Philipp Rahe, Osnabrück University
School of Physics
