Like a tiny needle in a sprawling hay field, a ten-million -three-meter single crystal grain found in a wellbore sample drilled in central siberia had an unexpected chemical composition.
A special x-ray technique at the Berkeley Lab's Lawrence Berkeley National Laboratory confirmed the uniqueness of the sample and paved the way for its formal recognition as a newly discovered mineral: ognitite.
Based on this success, the research team is using Berkeley Lab's Advanced Light Source (ALS) technology to study other tiny samples of promising candidates for new mineral discoveries. The ALS is a synchrotron that generates X-rays and other types of light for dozens of simultaneous experiments.
"The difficulty is that these minerals can be extremely rare and available only in very small amounts," said Nobumichi Tamura, a collaborator of ALS, involved in adapting the experimental technique (known as X-ray Laue microdiffraction ( and also micro-Laue X-ray diffraction)) to study tiny crystal samples, including minerals. Tamura was involved in the discovery of the ognitite and is now working with the same team to study other samples.
Taking up the "desperate cases"
The structure of the ognitite mineral and other properties are described in detail in a study published in May in Mineralogical Magazine and also documented in European Journal of Mineralogy . The study also describes a new, cobalt-rich mineral variety – referred to as the "Cobaltian Maucherite" – that Tamura researched using the same technique at ALS.
"We investigate cases where no conventional techniques can work," Tamura said. "These are the desperate cases."
He added, "For years, I've been interested in developing this technique specifically for identifying new minerals, as there are occasional researchers who have an unknown material that they can not resolve with any of the conventional techniques." Oognitit and Cobaltian Maucherite have so far only been identified as individual samples.
The form of X-ray Laue microdiffraction used at ALS becomes a tightly focused X-ray beam that spans a range of energies to study the atomic structure of materials down to the smallest detail. The beam is focused to one-hundredth of the diameter of a human hair.
In conventional single-crystal X-ray diffraction, crystal specimens are typically rotated in an X-ray beam with a given energy to aid in the resolution of their atomic structure, so Tamura extract them from surrounding materials without damaging the crystals. Techniques such as electron diffraction, single-crystal X-ray diffraction, and powder X-ray diffraction are usually out of the question.
The ALS technique scans the entire sample without having to rotate the crystal, separating it from its environment, or otherwise preparing it for study.
The entire scan is completed in minutes, though data analysis for this technique is far more complex than conventional diffraction and requires significant processing power. Researchers use computational clusters at the Berkeley Lab's National Energy Research Scientific Computing Center (NERSC) and its computer research department to process the data from the Laue microdiffraction experiments.
Catherine Dejoie, now beamline scientist at the European Synchrotron Radiation Facility (ESRF), was specifically recruited as a postdoctoral fellow at ALS in 2009 to develop a method for analyzing the data from Laue microdiffraction technology to resolve the atomic structure of materials. She worked closely with Tamura.
Chemical evidence in a tiny sample
Andrei Barkov, director of the Industrial and Arch Mineralogy Research Laboratory at Cherepovets State University in Russia, led the international team with the ognitite discovery and was the lead author of the ognitite study.
This team included Tamura and Camelia Stan – Stan was a researcher at ALS who participated in the ognitite study but has since left Berkeley Lab. Elise Grenot, a student researcher at the French engineering school École Nationale Supérieure de Techniques Avancées (ENSTA), now supports Tamura in the last round of candidates for new mineral experiments at the ALS.
Barkov learned of the technique developed on
Berkeley Lab through his connection to Björn Winkler, a professor at the Goethe University Frankfurt, who was familiar with the ALS technique.
Barkov has been involved in several other successful mineral discoveries, including studies that led to the formal recognition of Tatyanait, Edgarit, Laflammeit and Menshikovit as new minerals. However, the sample, now known as ognitite, was difficult to confirm as a new mineral, although its chemistry appeared to be unique, Barkov noted.
"This mineral was thought to be potentially new bismuth due to its unusually enriched composition," he said. "We could only find a single specimen as a tiny grain, the grain is so small – so Nobu Tamura's micro-Laue contributions were so important." Experiments at the ALS for the second time to receive the recognition of ohnitite as a unique mineral from the Commission for New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA). The IMA reported 5,413 recognized minerals as of November 2018, and the list grows by 30 or more minerals each year after review and approval by the Commission.
Ognitite contains nickel, bismuth and tellurium. The study finds that its crystal structure resembles a mineral called melonite, which also consists of nickel and tellurium, but is not associated with a high concentration of bismuth. And OGNITIT is chemically similar to Tellurohuchecornite mineral, which consists of nickel, bismuth, tellurium and sulfur.
New mineral named after Ognit Mineral Complex in Siberia The team's first choice was to call it "Baikalite" after Lake Baikal, which is located in the region where the new mineral was discovered, but this one Name was not approved by the IMA. Instead, the Commission favored "ognitite" as the mineral find comes from a location known as the Ognit Ultramafic Complex in the Siberian Sayan Mountains.
This geological formation is known to be rich in metal deposits, including rare platinum group elements. Nickel and chrome.
The Cobaltian Maucherite sample was obtained in the same Ognite complex of nickel-rich arsenides and had a diameter of only 20 millionths of a meter. Due to its size and rarity "it could only be structurally characterized by the micro-Laue technique".
His team researches this formation in other parts of Russia and can study the rock formations of special interest varying in size from about one kilometer to several tens of kilometers.
"We collect and examine in detail thousands of rock samples and ore samples and many other mineral grains," he said. "As a result of these efforts, individual grains of potentially new minerals can be found."
His team typically uses optical microscopes, Scanning Electron Microscopes, a technique known as energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy. and conventional X-ray diffraction to investigate mineral samples collected over decades.
From Russia to ALS
Barkov turned to Björn Winkler to find out if he can make a plastic "Professor Winkler has a solid background and suitable facilities in his lab to make new connections to synthesize that are comparable to potentially new minerals, "Barkov said. Winkler had already established a collaboration with Tamura, and Barkov then turned to Tamura to investigate the possibility of examining the ognitite sample at the ALS.
Dejoie helped develop the data analysis methods to support the use of the ALS technique The study of the structure of tiny crystals has returned to the ALS almost every year to experiment with this technique and improve data analysis methods. She said that in her own research, she now uses the technique for time-resolved experiments to track the transition of materials from one state of matter to another.
While the X-ray Laue microdiffraction is not unique among the synchrotron light sources of the world, Dejoie and Tamura noted that its specialized application to the ALS and the maturity of its data analysis methods are unique.
"We began to look at really small crystals – crystals that can not be seen in a classic setup." Dejoie remembered.
She noted that the technique can be used to determine the timing of processes such as chemical reactions and structural material changes.
The Laue microdiffraction technique she worked on "The ALS is a really interesting alternative to electron diffraction," said Dejoie, or at least a complementary tool to study the crystal structure, as it can quickly capture a whole high-precision data set.
She noted that an adaptation of Laue microdiffraction might also be useful for crystal studies on light sources known as X-ray free-electron lasers (XFELs) that exhibit ultrashort, bright pulses.
"It's funny to see the parallel – we've already used a similar type of approach," to characterize the structure of crystals in one go, without having to rotate them or align them in a certain way before doing so in XFEL Studies was tried.
In an XFEL technique known as "serial crystallography" phy, "Many crystal samples are streamed into the path of X-ray pulses with narrow energy." In these experiments, information is obtained from individual X-ray pulses directed to randomly oriented crystals of the same sample type
Dejoie was the lead author of a 2015 study detailing the diffraction of Laue The technique of using a high-energy X-pulse to single or multiple randomly oriented crystals simultaneously could be adapted for use with XFELs as a new "snapshot" approach for conventional serial crystallography.
It was gratifying to learn that the synchrotron-based technique for the Laue microdiffraction, which they used at the ALS developed, was helpful to confirm a new mineral. "It's always good when you see that something you have worked on, arouses interest. It means that it is spreading and that more people may be working on it. "
ALS and NERSC are both DOE Office of Science User Facilities.
The team that participated in the ognitite discovery included researchers from the University of Florence in Italy, the Siberian Federal University in Russia, McGill University in Canada, and the Natural History Museum in the UK The ALS is supported by the DOE Office of Basic Energy Science, and some of the people involved in the study were funded by the Russian Foundation for Basic Research and the UK Research Council for the Natural Environment.
A new level of seismic understanding
Andrei Y. Barkov et al. Ognitite, NiBiTe, a new mineral species, and Cobalt Maucherite from the Ognit-Ultramafic Complex, Eastern Sayans, Russia, Mineralogical Magazine (2019). DOI: 10.1180 / mgm.2019.31
Mineral discovery made easier: X-ray technology illuminates tiny, rare crystals (2019, 19 June)
retrieved on June 20, 2019
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