{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T16:14:22Z","timestamp":1781021662861,"version":"3.54.1"},"reference-count":43,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2019,5,14]],"date-time":"2019-05-14T00:00:00Z","timestamp":1557792000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Due to the rapidly increasing use of energy-efficient technologies, the need for complex materials containing rare earth elements (REEs) is steadily growing. The high demand for REEs requires the exploration of new mineral deposits of these valuable elements, as recovery by recycling is still very low. Easy-to-deploy sensor technologies featuring high sensitivity to REEs are required to overcome limitations by traditional techniques, such as X-ray fluorescence. We demonstrate the ability of laser-induced fluorescence (LIF) to detect REEs rapidly in relevant geological samples. We introduce two-dimensional LIF mapping to scan rock samples from two Namibian REE deposits and cross-validate the obtained results by employing mineral liberation analysis (MLA) and hyperspectral imaging (HSI). Technique-specific parameters, such as acquisition speed, spatial resolution, and detection limits, are discussed and compared to established analysis methods. We also focus on the attribution of REE occurrences to mineralogical features, which may be helpful for the further geological interpretation of a deposit. This study sets the basis for the development of a combined mapping sensor for HSI and 2D LIF measurements, which could be used for drill-core logging in REE exploration, as well as in recovery plants.<\/jats:p>","DOI":"10.3390\/s19102219","type":"journal-article","created":{"date-parts":[[2019,5,14]],"date-time":"2019-05-14T10:42:33Z","timestamp":1557830553000},"page":"2219","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Fast 2D Laser-Induced Fluorescence Spectroscopy Mapping of Rare Earth Elements in Rock Samples"],"prefix":"10.3390","volume":"19","author":[{"given":"Peter","family":"Seidel","sequence":"first","affiliation":[{"name":"Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8464-2331","authenticated-orcid":false,"given":"Sandra","family":"Lorenz","sequence":"additional","affiliation":[{"name":"Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas","family":"Heinig","sequence":"additional","affiliation":[{"name":"Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6200-2704","authenticated-orcid":false,"given":"Robert","family":"Zimmermann","sequence":"additional","affiliation":[{"name":"Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ren\u00e9","family":"Booysen","sequence":"additional","affiliation":[{"name":"Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany"},{"name":"School of Geosciences, University of the Witwatersrand, Johannesburg 2000, South Africa"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1403-395X","authenticated-orcid":false,"given":"Jan","family":"Beyer","sequence":"additional","affiliation":[{"name":"Technische Universit\u00e4t Bergakademie Freiberg, Institute of Applied Physics, Leipziger Stra\u00dfe 23, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johannes","family":"Heitmann","sequence":"additional","affiliation":[{"name":"Technische Universit\u00e4t Bergakademie Freiberg, Institute of Applied Physics, Leipziger Stra\u00dfe 23, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4383-473X","authenticated-orcid":false,"given":"Richard","family":"Gloaguen","sequence":"additional","affiliation":[{"name":"Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2019,5,14]]},"reference":[{"key":"ref_1","unstructured":"Gambogi, J. (2017). Rare Earths, Mineral Commodity Summaries 2017."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"188","DOI":"10.1080\/00387010.2015.1118127","article-title":"Development of an Online X-Ray Fluorescence Analysis System for Heavy Metals Measurement in Cement Raw Meal","volume":"49","author":"Qing","year":"2015","journal-title":"Spectrosc. Lett."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1016\/j.ifacol.2015.10.089","article-title":"Fast mineral identification using elemental LIBS technique","volume":"48","author":"Khajehzadeh","year":"2015","journal-title":"IFAC-PapersOnLine"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Kruse, F., Weatherbee, O., Peppin, W., Bedell, R., Calvin, W., and Taranik, J.V. (2010). HSI Mineral Mapping from Airborne, Outcrop, and Drill-Core Perspectives. Proc. SPIE, 7687.","DOI":"10.1117\/12.855445"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Zimmermann, R., Brandmeier, M., Andreani, L., Mhopjeni, K., and Gloaguen, R. (2016). Remote Sensing Exploration of Nb-Ta-LREE-Enriched Carbonatite (Epembe\/Namibia). Remote Sens., 8.","DOI":"10.3390\/rs8080620"},{"key":"ref_6","first-page":"219","article-title":"Visible to shortwave infrared reflectance spectroscopy of rare earth element minerals","volume":"3","author":"Turner","year":"2015","journal-title":"Br. Columbia Geol. Surv. Pap."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"641","DOI":"10.2113\/econgeo.111.3.641","article-title":"On the feasibility of imaging carbonatite-hosted rare earth element deposits using remote sensing","volume":"111","author":"Neave","year":"2016","journal-title":"Econ. Geol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.chemgeo.2015.09.001","article-title":"Laser-induced REE3+ photoluminescence of selected accessory minerals\u2014An \u201cadvantageous artefact\u201d in Raman spectroscopy","volume":"415","author":"Lenz","year":"2015","journal-title":"Chem. Geol."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Gaft, M., Reisfeld, R., and Panczer, G. (2015). Modern Luminescence Spectroscopy of Minerals and Materials, Springer. [2nd ed.].","DOI":"10.1007\/978-3-319-24765-6"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Fuchs, M.C., Gloaguen, R., Beyer, J., Jakob, S., and Heitmann, J. (2016, January 21\u201324). Emission spectroscopy for the identification of rare earth elements using laser-induced photoluminescence. Proceedings of the 2016 8th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), Los Angeles, CA, USA.","DOI":"10.1109\/WHISPERS.2016.8071681"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Lorenz, S., Beyer, J., Fuchs, M., Seidel, P., Turner, D., Heitmann, J., and Gloaguen, R. (2019). The Potential of Reflectance and Laser Induced Luminescence Spectroscopy for Near-Field Rare Earth Element Detection in Mineral Exploration. Remote Sens., 11.","DOI":"10.3390\/rs11010021"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"861","DOI":"10.3749\/canmin.46.4.861","article-title":"Xenotime-(Y) from carbonatite dykes at Lofdal, Namibia: Unusually low LREE:HREE ratio in carbonatite, and the first dating of xenotime overgrowths on zircon","volume":"46","author":"Wall","year":"2008","journal-title":"Can. Mineral."},{"key":"ref_13","unstructured":"Williams-Jones, A.E., Wollenberg, R., and Bodeving, S. (2015, January 13\u201314). Hydrothermal Fractionation of the Rare Earth Elements and the Genesis of the Lofdal REE Deposit. Proceedings of the Symposium on Strategic and Critical Materials 2015, Victoria, BC, Canada."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1016\/j.lithos.2016.11.024","article-title":"Carbonate\u2013silicate melt immiscibility, REE mineralising fluids, and the evolution of the Lofdal Intrusive Suite, Namibia","volume":"268","author":"Bodeving","year":"2017","journal-title":"Lithos"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"596","DOI":"10.2138\/am-2016-5502CCBY","article-title":"Evidence for dissolution-reprecipitation of apatite and preferential LREE mobility in carbonatite-derived late-stage hydrothermal processes","volume":"101","author":"Styles","year":"2016","journal-title":"Am. Mineral."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Unger, G., Zimmermann, R., and Gloaguen, R. (2018). 3D Modeling of the Epembe (Namibia) Nb-Ta-P-(LREE) Carbonatite Deposit: New Insights into Geometry Related to Rare Metal Enrichment. Minerals, 8.","DOI":"10.3390\/min8120600"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1144\/geochem2017-033","article-title":"Major and trace element geochemistry of the European Kupferschiefer\u2014An evaluation of analytical techniques","volume":"18","author":"Rahfeld","year":"2018","journal-title":"Geochem. Explor. Env. A"},{"key":"ref_18","first-page":"33","article-title":"Automated scanning electron microscope based mineral liberation analysis an introduction to JKMRC\/FEI mineral liberation analyser","volume":"2","author":"Gu","year":"2003","journal-title":"J. Miner. Mater. Char. Eng."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"310","DOI":"10.1016\/j.minpro.2006.07.018","article-title":"Modem SEM-based mineral liberation analysis","volume":"84","author":"Fandrich","year":"2007","journal-title":"Int. J. Miner. Process."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"527","DOI":"10.1017\/S1431927617000460","article-title":"Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis","volume":"23","author":"Bachmann","year":"2017","journal-title":"Microsc. Microanal."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Reisfeld, R. (1975). Radiative and non-radiative transitions of rare-earth ions in glasses. Rare Earths. Structure and Bonding, Springer.","DOI":"10.1007\/BFb0116557"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Hull, R., Parisi, J., OsgoodJr, R.M., Warlimont, H., Liu, G., and Jacquier, B. (2005). Spectroscopic Properties of Rare Earths in Optical Materials, Springer.","DOI":"10.1007\/3-540-28209-2"},{"key":"ref_23","first-page":"1","article-title":"Crystal field effects in rare earth systems","volume":"15","year":"1980","journal-title":"J. Magn. Magn. Mater."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1103\/RevModPhys.25.167","article-title":"Crystal Field Theory in the Rare Earths","volume":"25","author":"Elliott","year":"1953","journal-title":"Rev. Mod. Phys."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Marfunin, S.A. (1979). Spectroscopy, Luminescence and Radiation Centers in Minerals, Springer.","DOI":"10.1007\/978-3-642-67112-8"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1016\/S0168-583X(01)00354-8","article-title":"Structural point defects in \u201cIceland spar\u201d calcite","volume":"181","author":"Habermann","year":"2001","journal-title":"Nucl. Instrum. Methods Phys. Res. B"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1007\/s00710-002-0227-y","article-title":"Cathodoluminescence of synthetic and natural calcite: The effects of manganese and iron on orange emission","volume":"78","author":"Cazenave","year":"2003","journal-title":"Miner. Petrol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"639","DOI":"10.1007\/s00269-012-0518-8","article-title":"The luminescence properties of rare-earth ions in natural fluorite","volume":"39","author":"Czaja","year":"2012","journal-title":"Phys. Chem. Minerals"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"980","DOI":"10.1016\/j.rinp.2017.02.015","article-title":"Grains size and shape dependence of luminescence efficiency of Lu2O3:Eu thin screens","volume":"7","author":"Seferis","year":"2017","journal-title":"Results Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2713","DOI":"10.1016\/0016-7037(92)90355-M","article-title":"Laser-excited fluorescence of rare earth elements in fluorite: Initial observations with a laser Raman microprobe","volume":"56","author":"Burruss","year":"1992","journal-title":"Geochim. Cosmochim. Acta"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1016\/S0925-3467(97)00042-6","article-title":"Accommodation of rare-earths and manganese by apatite","volume":"8","author":"Gaft","year":"1997","journal-title":"Opt. Mat."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"L1","DOI":"10.1016\/j.jallcom.2004.06.036","article-title":"Preparation and luminescence properties of Eu3+-doped MSnO3 (M = Ca, Sr and Ba) perovskite materials","volume":"387","author":"Lu","year":"2005","journal-title":"J. Alloys Compd."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1016\/S0022-2313(96)00114-7","article-title":"Laser-induced luminescence of rare-earth elements in natural fluor-apatites","volume":"69","author":"Reisfeld","year":"1996","journal-title":"J. Lumin."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.gexplo.2013.08.001","article-title":"Rare Earth Elements: The role of geology, exploration, and analytical geochemistry in ensuring diverse sources of supply and a globally sustainable resource","volume":"133","author":"Foley","year":"2013","journal-title":"J. Geochem. Explor."},{"key":"ref_35","first-page":"356","article-title":"The visible region absorption spectra of rare earth minerals","volume":"50","author":"Adams","year":"1965","journal-title":"Am. Mineral."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"857","DOI":"10.2113\/gsecongeo.81.4.857","article-title":"Spectral reflectance of carbonatites and related alkalic igneous rocks; selected samples from four North American localities","volume":"81","author":"Rowan","year":"1986","journal-title":"Econ. Geol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1335","DOI":"10.2138\/am.2014.4674","article-title":"Visible and short-wave infrared reflectance spectroscopy of REE fluorocarbonates","volume":"99","author":"Turner","year":"2014","journal-title":"Am. Mineral."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Turner, D., Rivard, B., and Groat, L. (2014, January 13\u201318). Rare earth element ore grade estimation of mineralized drill core from hyperspectral imaging spectroscopy. Proceedings of the 2014 IEEE Geoscience and Remote Sensing Symposium, Quebec City, QC, Canada.","DOI":"10.1109\/IGARSS.2014.6947520"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"359","DOI":"10.1016\/0012-821X(70)90136-6","article-title":"Rare earth concentrations in zircons and apatites and their host dacites and granites","volume":"9","author":"Nagasawa","year":"1970","journal-title":"Earth Planet. Sci. Lett."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"489","DOI":"10.1016\/0169-1368(94)00015-G","article-title":"Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types","volume":"9","author":"Frietsch","year":"1995","journal-title":"Ore Geol. Rev."},{"key":"ref_41","first-page":"167","article-title":"The effects of Manganese(II) and Iron(II) on the cathodoluminescence signal in synthetic apatite","volume":"63","author":"Filippelli","year":"1993","journal-title":"J. Sedimen. Res."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"601","DOI":"10.1111\/j.1365-3091.1981.tb01924.x","article-title":"The control of cathodoluminescence in dolomite by iron and manganese","volume":"28","author":"Pierson","year":"1981","journal-title":"Sedimentology"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"5160","DOI":"10.3390\/rs70505160","article-title":"Hyperspectral REE (Rare Earth Element) Mapping of Outcrops\u2014Applications for Neodymium Detection","volume":"7","author":"Boesche","year":"2015","journal-title":"Remote Sens."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/10\/2219\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:51:42Z","timestamp":1760187102000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/10\/2219"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,5,14]]},"references-count":43,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2019,5]]}},"alternative-id":["s19102219"],"URL":"https:\/\/doi.org\/10.3390\/s19102219","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,5,14]]}}}