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the length of the trail is suited to a confident beginner or intermediate rider (and kids over the age of 10) Advanced mountain bikers may want to try their luck the mine’s more challenging track dubbed the “Black Hole,” etched ominously into the mine’s even-narrower crevices Marko pauses to point out some of the mine’s features: giant caverns of natural beauty rusting buckets of ore sitting for decades and which attest to the day-to-day difficulties of working a mine Here and there he points to surviving veins of white rust-brown wulfenite still embedded in the walls (an on-site museum highlights the many metals and minerals that have been found inside the mine) After a little more than an hour of riding we re-emerge smiling – if temporarily blinded ­– into the bright summer sunshine and in my mind I picture a typical ride with comfortable seats and windows Matej and I climb into a tiny box of a carriage each no wider than the length of my arm and only a few feet long were once used to carry as many as eight miners at a time as deep as 1.8 miles (3km) below the surface It’s hard to imagine today – the carriage feels cramped with just the three of us inside I have a deep appreciation for the educational aspect of our visit was a daily reality for thousands of men who once worked these seams and descend a further 600 steps to the chamber’s low-lying pools of fresh water we pause momentarily in a heated dressing room to don chest-high waders that will protect us from the chilly (43°F / 6°C) water we walk into the water and fetch our kayaks we’re free to aim our boats wherever we want and to follow the narrow channels wherever they lead the space feels unexpectedly airy and peaceful; the silence is broken only by our laughter and the sounds of paddles dipping into the clear water the water throws back shades of green and blue I feel a temporary urge to dive in (and then I remember the temperature) It dawns on me I’ll likely never forget this moment This story was crafted collaboratively between Slovenia Tourism and Lonely Planet. Both parties provided research and curated content to produce this story. We disclose when information isn’t ours. Determines the concept, provides briefing, research material, and may provide feedback. We provide expertise, firsthand insights, and verify with third-party sources when needed. Metrics details A Publisher Correction to this article was published on 02 May 2024 This article has been updated we introduce a novel approach using correlative analysis techniques to unravel detailed insights into the environmental influences on crystal growth Tabular and bipyramidal wulfenite samples from the Mežica mine in north-eastern Slovenia were analysed to combine the morphological aspects of crystal growth with the atomic-resolution reconstruction of the positions of lead (Pb) and molybdenum (Mo) atoms in the parent crystal lattice These combined data also allow us to present the formation mechanism that enables the development of bipyramidal or tabular morphologies in wulfenite The bipyramidal and tabular crystals are chemically pure wulfenite (PbMoO4) as confirmed by various advanced diffraction and spectroscopy techniques The differences in the morphologies can be attributed to compositional changes during precipitation from a meteoric solution and thus we propose a growth mechanism consisting of three different phases of growth This innovative approach emphasises the importance of understanding the origin of crystal habits as can help to decipher how external influences can affect the crystal structure and its surface leading to the dissolution of preferred surfaces and the selective release of Pb and Mo we introduce wulfenite crystals with a wide range of crystal habits from the Mežica area (Republic of Slovenia) Wulfenite crystals provide an excellent opportunity to study and understand the relationship between their crystal habits and the underlying crystal chemistry These results confirm that the precipitation of the wulfenite crystals from Mežica occurred at ambient temperature and atmospheric pressure which is consistent with the conditions of the wulfenites grown by Vesselinov in the laboratory The presented study aims to define well-linked analytical information across multiple length-scale orders from the millimetre-scale morphological aspects of crystal growth to the micrometre-scale chemical composition of the crystal leading to an atomically resolved reconstruction of the positions of Pb and Mo atoms in the lattice of the parent crystal We hypothesised that the combined data would allow us to formulate the mechanism leading to the development of bipyramidal or tabular crystal habits for wulfenite using Vesselinov’s findings as a theoretical basis This innovative approach and comprehensive methodology highlights the importance of understanding the origin of crystal habits and their relationship with environment this knowledge can help to decipher how external influences can affect the crystal structure and its surface leading to the dissolution/weathering of preferential surfaces and consequently to the selective release of Pb and Mo This knowledge is therefore also particularly valuable for environmental scientists and various technical fields Schematic representation of the two most common morphological varieties of wulfenite crystals Ideal wulfenite crystal structure viewed along the (c) [100] and (d) [001] zone axes Electron-backscatter diffraction (EBSD) analysis was performed using an SEM FSEM JEOL 7600F equipped with an EBSD detector The obtained data were processed using the ICSD 2003 database for wulfenite as a reference Atomically resolved high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images were acquired via a probe Cs aberration correction transmission electron microscope (TEM) (JEM-ARM 200CF; JEOL also equipped with a JEOL Centurio 100 mm2 EDXS detector operates at 200 keV and provides a spatial resolution of 0.08 nm in STEM mode EDXS elemental maps were produced in STEM mode (STEM-EDXS) to evaluate the elemental distribution with a high spatial resolution The specimen preparation for the SEM/EDXS and TEM analyses involved cutting crystal samples along the principle crystallographic zone axes which was determined using the EBSD technique SEM/EDXS specimens were cut parallel to [001] thin electron-transparent lamellae from both bipyramidal and tabular specimens of wulfenite were produced by using a focused ion beam scanning electron microscope (FIB-SEM; Helios NanoLab 600i dual beam system The TEM electron transparent lamellae were cut parallel to the (100) atomic plane On the left is a photo of a heap of tabular wulfenites from Mežica On the right are the clusters and specimens used in this study (a) Cluster of orange translucent bipyramidal crystals (b) bipyramidal specimen taken from the cluster (c) cluster of yellowish translucent tabular wulfenite crystals and (d) tabular specimen taken from the cluster shown in panel c The crystal structure constructed from the refinement data (a) View from [001] zone axis; (b) view from [111] zone (a) and (b) Low-magnification SEM backscattered electron images showing layers of inclusions in the two bipyramidal specimens where the growth change from tabular to bipyramidal can be observed on both images; the zone axis is [100] (c) Higher magnification SEM BSE image showing a cluster of inclusions The image is a colour-coded phase map created from EDXS analysis data focusing on the rare descloizite inclusion The orange colour represents the wulfenite phase (a) Bipyramidal and tabular (b) crystals of the wulfenite sample The lattice planes are marked on the crystals The FIB-cut [100]-oriented lamella is shown in the inset obtained from tabular crystal and O obtained from the same area as the presented ADF image showing a homogeneous elemental distribution in the studied area (d) Constructed atomic model of the MoPbO4 crystal (data from SCXRD analysis) projected along the a-axis and 16f mark the Wyckoff positions of the corresponding Mo unprocessed HAADF-STEM image at high magnification projected along the a-axis ([100] zone axis) The high-resolution HAADF-STEM image with the superimposed atomic model viewed along the [100] zone axis is displayed in the inset The lattice spacing between the atomic planes along the c-axis is shown (3.15 Å) Twinning or structure defects can be ruled out as a possible explanation for the differences in the external morphology of wulfenite as they could not be detected by SCXRD or HAADF-STEM We would also expect to be able to detect these agents in the atomic resolution HAADF-STEM images particularly outside of the thin inclusion-rich layer mentioned earlier these images show no defects or impurities supporting our conclusion that surface coverage did not significantly affect crystal growth the possible presence of impurities in our study does not seem to alter the crystal symmetries of the bipyramidal and tabular samples to the extent that they could be considered as different crystallographic phases since both morphologies belong to space group I41/a The changes in concentrations mark the beginning and end of each growth phase of the wulfenite crystals 3. In the third phase, the ratio of CPb/CMoO4 in the solutions is greater than 1, which promotes the growth of wulfenite, especially in the directions < 001 > , so that tetragonal pyramids {101} began to grow on the tabular base of the crystals, giving them bipyramidal morphology (Fig. 4: Growth of {001} inhibited Some crystals retain their tabular morphology during the third phase It should be noted that carbonate inclusions are also present in these crystals in the form of bands suggesting that they precipitated from the same solutions as bipyramidal wulfenite but did not experience surface growth due to factors such as orientation or spatial limitations that did not allow growth in the < 001 > directions This explains why some clusters show both morphologies although the crystals are spatially very close to each other separated by distances of at most a few millimetres Wulfenite crystals from the Mežica Mine exhibit bipyramidal and tabular morphologies The bipyramidal crystals consist of a tabular base and two tetragonal pyramids that grow on opposite sides of the base These inclusions are often arranged in layers These layers occur throughout the tabular crystals and in the tabular base of the bipyramidal crystals The SCXRD analysis confirmed that both forms belong to the same space group The analysis also confirmed the pure wulfenite compositions determined from the EDXS which were further confirmed by the HAADF-STEM analysis The differences in morphology can therefore be attributed to changes in composition (concentrations of Pb2+ and MoO42−) during precipitation from the meteoric solution rather than to differences in lattice geometry defects such as twinning or surface capping by carbonates We propose a growth mechanism that consists of three phases of growth: the concentration ratio between CPb and CMoO4 in the solution is lower than 1 which favours the growth of tabular crystals carbonates precipitated from the solutions and are present as inclusions in the wulfenite Carbonate precipitation occurs incidental with the change in the concentrations of Pb2+ and MoO42− (CPb/CMoO4 ratio becomes greater than 1) In the third phase the CPb/CMoO4 > 1 ratio favours the pyramidal growth of wulfenite crystals As some of the tabular crystals remained protected from the new influx of solutions The data are available in the Department of Geology Faculty of Natural Sciences and Engineering University of Ljubljana and in the Department for Nanostructured Materials Jozef Stefan Institute (contact person Nastja Rogan Šmuc A Correction to this paper has been published: https://doi.org/10.1038/s41598-024-60770-8 Uptake of elements from a biological point of view Evolution of crystal structure of PbMoO4 between 5 and 300 K: A low temperature powder neutron diffraction study A new structural model for Pb-deficient PbWO4 An explanation for the origin of hemihedrism in wulfenite: The single-crystal structures of I 4 1/a and I tungstenian wulfenites Cleavage nature and surface appearances of wulfenite by first-principles calculations and experimental measurment Theoretical analysis of changes in habit of growing crystals in response to variable growth rates of individual faces A study on the kinetic conditions corresponding to the growth of crystals of different morphologies On the symmetry of wulfenite (Pb[MoO4]) from Mežica (Slovenia) Hemimorphic wulfenite crystals from Mežica The wulfenite—stolzite series: Centric or acentric structures? Analysis of solid solutions stability in scheelite-type molybdates and tungstates Kinetically induced morphological changes in laboratory-grown wulfenite crystals [Older versions (pre-1997) should refer to Siemens Analytical X-ray Instruments Inc SHELXT–integrated space-group and crystal-structure determination geokemične in mineraloške značilnosti rude in prikamenine svinčevo-cinkovih orudenj mežiškega rudišča Characterization of “sandwich” wulfenite from the Ojuela mine Mexico: Evidence of preferred secondary nucleation on selected wulfenite faces Surface capping agents and their roles in shape-controlled systhesis of colloidal metal nanocrystals Twinning and epitaxial growth of taaffeite-type modulated structures in BeO-doped MgAl2O4 The significance of wulfenite morphology as shown on crystals from Mezica Download references This work was carried out with the financial support of the Slovenian Research and Innovation agency and as part of the ERC complementary scheme N1-0164 (Molybdenum geobiochemical cycle in rocks and sediments) conducted analyses and interpreted the data; N.G The authors declare no competing interests Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations The original online version of this Article was revised: The original version of this Article contained errors in the Figure legends of Figures 1 The legends of these Figures were inadvertently switched Full information regarding the corrections made can be found in the correction for this Article Download citation DOI: https://doi.org/10.1038/s41598-024-60043-4 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page.