An international research team involving scientists has described the process of growing three-dimensional manganese dendrites
The team, involving scientists from the University of Vienna, the Faculty of Physics of the University of Warsaw and the University of Edinburgh, found that it occurs through accretion of manganese oxide nanoparticles.
Understanding the dynamics of the growth of three-dimensional mineral dendrites is important for various fields of science – physics, geology, material sciences and even the study of extraterrestrial environments.
Not only are scientists gaining valuable insights into the history of rocks and minerals, the knowledge can also be used in industry, for example in the production of synthetic materials with new properties.
When we think of minerals, we often imagine perfectly formed, symmetrical structures. However, in Nature, there are instances where they take on more intricate and unexpected shapes.
A recent study has shed light on the growth dynamics of mineral dendrites providing the pioneering insights into their formation and the geological history they encode.
This discovery challenges conventional crystallisation pathways and offers a fascinating glimpse into the complex world of mineral formation.
Unlike the metallic or crystalline dendrites that form from supercooled melts, mineral dendrites are a result of unstable aqueous growth processes driven by fluid motion and chemical concentration gradients.
Manganese dendrites, in particular, are known to develop as two-dimensional structures on rock surfaces.
However, until now, the growth processes of three-dimensional dendrites have remained largely enigmatic.
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Growth of dendrites
The study focused on natural dendrites formed in clinoptilolite-tuffs (zeolites), a type of compacted, porous volcanic tuff.
Dawid Wos, a student at the University of Warsaw’s Faculty of Physics and creator of the numerical model used in the study, said: “By combining high-resolution X-ray and electron-based imaging techniques with numerical modelling, we were able to unlock the secrets hidden within these intricate mineral formations.”
The researchers discovered that the growth of dendrites occurred through the accretion of Mn oxide nanoparticles to the elongating structures.
Dr Zhaoliang Hou, of the Department of Geology of the University of Vienna and lead author of the publication, added: “These nanoparticles formed when Mn-rich fluids mixed with oxygenated pore-water, leading to the development of complex dendritic structures.
“Remarkably, the geometry of these dendrites recorded the hydro-geochemical history of the rock, including the concentration of ions, the volume of infiltrating fluid, and the number of fluid pulses.
“In essence, these 3D dendrites can serve as geological fingerprints, preserving a record of past environmental conditions.”
The study also highlighted a non-classical crystallisation pathway in which dendrite growth proceeds through the formation, diffusion, and attachment of Mn oxide nanoparticles.
This pathway challenges traditional views of crystal growth and emphasises the significance of particle attachment processes in the natural world.
It further aligns with the growing recognition of this mechanism as a vital and widespread type of crystal growth.
Important implications
There are important implications for various fields, including physics, geology, material science, and the study of extraterrestrial environments.
In particular, the latter aspect presents an exciting opportunity to explore the influence of micro-organisms on the growth of MnO dendrites.
By deciphering the complex processes behind their formation, scientists gain valuable insights into the history of rocks and minerals.
Furthermore, this research paves the way for further investigations into similar dendritic formations, such as gold/electrum dendrites.
Professor Piotr Szymczak of the University of Warsaw’s Faculty of Physics said: “The study of 3-D Mn dendrites has unveiled a captivating world of non-classical crystallisation pathways and the hidden stories recorded within geological structures.
“By combining advanced imaging techniques and numerical modelling, scientists have taken a significant step forward in unravelling the mysteries of these intricate mineral formations.
“As we delve deeper into the secrets of crystal growth, we open doors to a better understanding of Earth’s history and the fascinating mechanisms at play in the natural world.”
Image: Morphologies of the dendrite forest for different surface energies and manganese ion concentrations. Credit: Faculty of Physics, University of Warsaw.
