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Cu nanoparticle geometry as the key to bicolor behavior in Oregon sunstones: An application of LSPR theory in nanomineralogy

  • Chengsi Wang ORCID logo , Andy H. Shen , Peter J. Heaney , Aaron Palke , Ke Wang , Haiying Wang and Lore Kiefert
Published/Copyright: February 4, 2025
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American Mineralogist
From the journal American Mineralogist Volume 110 Issue 2

Abstract

The coloration mechanism of Oregon sunstone is a classic and controversial topic in mineralogy because of the unique coexistence of anisotropic (green-red) and isotropic (red) color zones within single feldspar crystals. After nearly 50 years of research, no models proposed to date have satisfactorily accounted for all observed optical phenomena. Here, we present high-resolution transmission electron microscopy analyses of samples prepared by focused ion beam extraction along specific crystal directions. In both the anisotropic and the isotropic color zones, we observed Cu nanoparticles (NPs) included within plagioclase but with different geometries. In the isotropic (red) zone, NPs were randomly distributed nano-spheres or nano-ellipsoids (8.7–12 nm in diameter) with an aspect ratio of 1–1.3. In contrast, in dichroic (green/red) zones, NPs were directionally aligned nano-rods (8.5–21 nm along the long axis) with an aspect ratio of ∼2.5. We applied localized surface plasmon resonance (LSPR) theory to simulate absorption spectra and developed a model to explain the observed optical properties. LA-ICP-MS and polarized UV-Vis spectroscopy were also performed to confirm our conclusions. This study systematically reveals the existence and optical influence of variably shaped metal-NP inclusions in feldspar crystals. Furthermore, it demonstrates the necessity of including LSPR in the canon of mineral coloration mechanisms. Cu-NP-bearing labradorite has been shown to exhibit third-order nonlinear optical properties, and approaches that incorporate NP shapes and sizes will assist in designing NP-embedded optical materials with tailored optical properties.

Keywords: Cu nanoparticles; Oregon sunstones; nano-inclusions; localized surface plasmon resonance; high-resolution transmission electron microscopy; plagioclase

Acknowledgments and Funding

We sincerely appreciate the valuable comments and suggestions from Zack Gainsforth and Brittany Cymes, which helped us to improve the quality of the manuscript. We thank Shane McClure from GIA for the sample and information support and George R. Rossman from the California Institute of Technology for important suggestions. We also thank Da Sun from Tianjin University of Technology and Jinyu Zheng from China University of Geosciences (Wuhan) for their help on crystal indexing. The authors acknowledge the financial support of the 2018 grant from Eduard Gübelin research scholarship, the GIA International Internship Program, the China Postdoctoral Science Foundation [2023M743293], the Basic and Applied Research Fund of Guangdong Province [2022A1515110780], and grant [CIGTXM-04-S202302] from the Center for Innovative Gem Testing Technology, China University of Geosciences (Wuhan). Peter J. Heaney acknowledges support from NSF EAR1925903.

References Cited

Adachi, S. (2012) The Handbook on Optical Constants of Metals in Tables and Figures, 684 p. World Scientific Publishing Company.Search in Google Scholar

Ahn, C.C. (2004) Transmission Electron Energy Loss Spectrometry in Materials Science and the EELS Atlas, 2nd Edition, 469 p. Wiley-VCH.Search in Google Scholar

Aitkens, I. and States, U. (1931) Feldspar gems: (Amazon stone, Moonstone, Sunstone, etc.). Sunstone. U.S. Dept. of Commerce, Bureau of Mines.Search in Google Scholar

Anonymous. (1934) Oregon sunstone. Oregon Mineralogist, 1, 4.Search in Google Scholar

Badur, C.B. (2022) An investigation of native copper in plagioclase, Lake and Harney Counties, 76 p. Master’s thesis, Auburn University.Search in Google Scholar

Blumer, H. (1925) Strahlungsdiagramme kleiner dielektrischer Kugeln. The European Physical Journal A, 32, 119–134, https://doi.org/10.1007/BF01331653.Search in Google Scholar

Borghese, F., Denti, P., and Saija, R. (2007) Scattering from Model Nonspherical Particles: Theory and Applications to Environmental Physics, 368 p. Springer.Search in Google Scholar

Borrelli, N. and Seward, T. (2012) Polarcor™ polarizing glasses. New Glass, 27, 27–35.Search in Google Scholar

Cai, J., Zhang, C., and Li, W.D. (2021) Dual-color flexible metasurfaces with polarization-tunable plasmons in gold nanorod arrays. Advanced Optical Materials, 9, 2001401, https://doi.org/10.1002/adom.202001401.Search in Google Scholar

Cheng, L., Zhu, G., Liu, G., and Zhu, L. (2020) FDTD simulation of the optical properties for gold nanoparticles. Materials Research Express, 7, 125009, https://doi.org/10.1088/2053-1591/abd139.Search in Google Scholar

Crane, C.C., Wang, F., Li, J., Tao, J., Zhu, Y., and Chen, J. (2017) Synthesis of copper-silica core-shell nanostructures with sharp and stable localized surface plasmon resonance. The Journal of Physical Chemistry C, 121, 5684–5692, https://doi.org/10.1021/acs.jpcc.6b11891.Search in Google Scholar

Dai, H., Yao, L., Cheng, H., and Han, J. (2020) Polarization-independent large third-order optical nonlinearity in centimeter-sized random-distributed gold nanorod arrays. The Journal of Physical Chemistry C, 124, 17237–17243, https://doi.org/10.1021/acs.jpcc.0c04780.Search in Google Scholar

Dake, C.H. (1938) The Gem Minerals of Oregon, 23 p. Oregon State Department of Geology and Mineral Industries.Search in Google Scholar

Doremus, R., Kao, S.-C., and Garcia, R. (1992) Optical absorption of small copper particles and the optical properties of copper. Applied Optics, 31, 5773–5778, https://doi.org/10.1364/AO.31.005773.Search in Google Scholar

Ewels, P., Sikora, T., Serin, V., Ewels, C.P., and Lajaunie, L. (2016) A Complete overhaul of the electron energy-loss spectroscopy and X-ray absorption spectroscopy database: Eelsdb.eu. Microscopy and Microanalysis, 22, 717–724, https://doi.org/10.1017/S1431927616000179.Search in Google Scholar

Fan, X., Zheng, W., and Singh, D.J. (2014) Light scattering and surface plasmons on small spherical particles. Light, Science & Applications, 3, e179, https://doi.org/10.1038/lsa.2014.60.Search in Google Scholar

Fraundorf, P. and Fei, L. (2004) Digital darkfield decompositions. Microscopy and Microanalysis, 10, 300–301, https://doi.org/10.1017/S1431927604886045.Search in Google Scholar

Freestone, I., Meeks, N., Sax, M., and Higgitt, C. (2007) The Lycurgus Cup—A Roman nanotechnology. Gold Bulletin, 40, 270–277, https://doi.org/10.1007/BF03215599.Search in Google Scholar

Gall, D. (2016) Electron mean free path in elemental metals. Journal of Applied Physics, 119(8), 085101, https://doi.org/10.1063/1.4942216.Search in Google Scholar

Gans, R. (1925) Strahlungsdiagramme ultramikroskopischer Teilchen. Annalen der Physik, 381, 29–38, https://doi.org/10.1002/andp.19253810103.Search in Google Scholar

Geitgey, R.P. (1987) Oregon sunstones. Oregon Geology, 49, 23.Search in Google Scholar

Grigorchuk, N.I. and Tomchuk, P.M. (2011) Optical and transport properties of spheroidal metal nanoparticles with account for the surface effect. Physical Review B, 84, 085448, https://doi.org/10.1103/PhysRevB.84.085448.Search in Google Scholar

Gunn, B.M. and Watkins, N.D. (1970) Geochemistry of the Steens Mountain Basalts, Oregon. Geological Society of America Bulletin, 81, 1497–1516, https://doi.org/10.1130/0016-7606(1970)81[1497:GOTSMB]2.0.CO;2.Search in Google Scholar

He, Y.J. (2015) Novel and high-performance LSPR biochemical fiber sensor. Sensors and Actuators B: Chemical, 206, 212–219, https://doi.org/10.1016/j.snb.2014.09.061.Search in Google Scholar

Hergert, W. and Wriedt, T., Eds. (2012) The Mie theory basics and application, 273 p. Springer.Search in Google Scholar

Hicks, O. (1997) Oregon sunstones; these sparklers are formed from lava flow. Rock & Gem, 27, 80.Search in Google Scholar

Hochella, M.F. (2008) Nanogeoscience: From origin to cutting-edge applications. Elements, 4, 373–379, https://doi.org/10.2113/gselements.4.6.373.Search in Google Scholar

Hofmeister, A.M. and Rossman, G.R. (1985) Exsolution of metallic copper from Lake County labradorite. Geology, 13, 644–647, https://doi.org/10.1130/0091-7613(1985)13<644:EOMCFL>2.0.CO;2.Search in Google Scholar

Jensen, A. (1982) The distribution of Cu across three basaltic lava flows from the Faeroe Islands. Bulletin of the Geological Society of Denmark, 31, 1–10, https://doi.org/10.37570/bgsd-1983-31-01.Search in Google Scholar

Jin, S., Sun, Z., and Palke, A.C. (2022) Color effects of Cu nanoparticles in Cu-bearing plagioclase feldspars. American Mineralogist, 107, 2188–2200, https://doi.org/10.2138/am-2022-8325.Search in Google Scholar

Kawabata, A. and Kubo, R. (1966) Electronic properties of fine metallic particles. II. Plasma resonance absorption. Journal of the Physical Society of Japan, 21, 1765–1772, https://doi.org/10.1143/JPSJ.21.1765.Search in Google Scholar

Kelly, K.L.L., Coronado, E., Zhao, L.L., and Schatz, G.C. (2003) The optical properties of metal nanoparticles: The influence of size, shape and dielectric environment. The Journal of Physical Chemistry B, 107, 668–677, https://doi.org/10.1021/jp026731y.Search in Google Scholar

Khlebtsov, N.G. (2013) T-matrix method in plasmonics: An overview. Journal of Quantitative Spectroscopy & Radiative Transfer, 123, 184–217.Search in Google Scholar

Khlebtsov, B., Khanadeev, V., Pylaev, T., and Khlebtsov, N. (2011) A new T-matrix solvable model for nanorods: TEM-based ensemble simulations supported by experiments. The Journal of Physical Chemistry C, 115, 6317–6323.Search in Google Scholar

Kiefert, L., Wang, C., Sintayehu, T., and Link, K. (2019) Sunstone labradoritebytownite from Ethiopia. The Journal of Geology, 36, 694–695.Search in Google Scholar

Kreibig, U. and Vollmer, M. (1995) Optical Properties of Metal Clusters, 535 p. Springer.Search in Google Scholar

Krzemnicki, M.S. (2004) Red and green labradorite feldspar from Congo. The Journal of Geology, 29, 15–23.Search in Google Scholar

Link, S. and El-Sayed, M.A. (1999) Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods. The Journal of Physical Chemistry B, 103, 8410–8426, https://doi.org/10.1021/jp9917648.Search in Google Scholar

Liz-Marazán, L.M. (2012) Nanometals formation and color. Materials Today, 7, 26–31.Search in Google Scholar

Long, N.J. and Petford-Long, A.K. (1986) In-situ electron-beam-induced reduction of CuO: A study of phase transformations in cupric oxide. Ultramicroscopy, 20, 151–159, https://doi.org/10.1016/0304-3991(86)90181-6.Search in Google Scholar

Lv, S., Du, Y., Wu, F., Cai, Y., and Zhou, T. (2022) Review on LSPR assisted photo-catalysis: Effects of physical fields and opportunities in multifield decoupling. Nanoscale Advances, 4, 2608–2631, https://doi.org/10.1039/D2NA00140C.Search in Google Scholar

Mie, G. (1908) Beiträge zur Optik trüber Medien, speziell kolloidaler Metallösungen. Annalen der Physik, 25, 377–445, https://doi.org/10.1002/andp.19083300302.Search in Google Scholar

Nassau, K. (2001) The Physics and Chemistry of Color: The Fifteen Causes of Color, 2nd Edition, 496 p. Wiley Interscience.Search in Google Scholar

Nicoletti, O., de la Peña, F., Leary, R.K., Holland, D.J., Ducati, C., and Midgley, P.A. (2013) Three-dimensional imaging of localized surface plasmon resonances of metal nanoparticles. Nature, 502, 80–84, https://doi.org/10.1038/nature12469.Search in Google Scholar

Nishida, N. and Kimata, M. (2002) Identification of microinclusions in the nanometer dimension by electron microprobe analysis—The chromonophores of colored sunstones. Japanese Magazine of Mineralogical and Petrological Sciences, 31, 268–274, https://doi.org/10.2465/gkk.31.268.Search in Google Scholar

Pay, D., Weldon, R., McClure, S., and Schumacher, K. (2013) Three occurrences of Oregon sunstone. Gems & Gemology, 49, 162–171, https://doi.org/10.5741/GEMS.49.3.162.Search in Google Scholar

Peterson, N.V. (1972) Oregon “sunstones”. The Ore Bin, 34, 197.Search in Google Scholar

Petryayeva, E. and Krull, U.J. (2011) Localized surface plasmon resonance: Nanostructures, bioassays and biosensing—A review. Analytica Chimica Acta, 706, 8–24, https://doi.org/10.1016/j.aca.2011.08.020.Search in Google Scholar

Pough, F.H. (1983) Heliolite, a transparent, facetable phase of calcic labradorite. Journal of Gemmology, 18, 503–514, https://doi.org/10.15506/JoG.1983.18.6.503.Search in Google Scholar

Quinten, M. (2011) Optical Properties of Nanoparticle Systems Mie and Beyond, 504 p. Wiley-VCH.Search in Google Scholar

Reyna, A.S. and de Araújo, C.B. (2017) High-order optical nonlinearities in plasmonic nanocomposites—A review. Advances in Optics and Photonics, 9, 720–761, https://doi.org/10.1364/AOP.9.000720.Search in Google Scholar

Rossman, G.R. (2014) Optical spectroscopy. Reviews in Mineralogy and Geochemistry, 78, 371–398, https://doi.org/10.2138/rmg.2014.78.9.Search in Google Scholar

Ruppin, R. (1975) Optical properties of small metal spheres. Physical Review B, 11, 2871–2876, https://doi.org/10.1103/PhysRevB.11.2871.Search in Google Scholar

Ruppin, R. (1986) Optical absorption of copper colloids in photochromic glasses. Journal of Applied Physics, 59, 1355–1359, https://doi.org/10.1063/1.336530.Search in Google Scholar

Stookey, S.D. (1949) Coloration of glass by gold, silver, and copper. Journal of the American Ceramic Society, 32, 246–249, https://doi.org/10.1111/j.1151-2916.1949.tb18957.x.Search in Google Scholar

Sun, L., Chen, P., and Lin, L. (2016) Enhanced molecular spectroscopy via localized surface plasmon resonance. In M.T. Stauffer, Ed., Applications of Molecular Spectroscopy to Current Research in the Chemical and Biological Sciences. InTech Open.Search in Google Scholar

Tira, C., Tira, D., Simon, T., and Astilean, S. (2014) Finite-difference time-domain (FDTD) design of gold nanoparticle chains with specific surface plasmon resonance. Journal of Molecular Structure, 1072, 137–143, https://doi.org/10.1016/j.molstruc.2014.04.086.Search in Google Scholar

van Der Zande, B.M.I., Böhmer, M.R., Fokkink, L.G.J., and Schönenberger, C. (2000) Colloidal dispersions of gold rods: Synthesis and optical properties. Langmuir, 16, 451–458, https://doi.org/10.1021/la9900425.Search in Google Scholar

Wang, C., Shen, A., Palke, A., and Heaney, P. (2019) Color Origin of the Oregon sunstone – The reabsorption and exsolurion of Cu inclusions. International Gemmological Conference, 71–74. Nantes, France.Search in Google Scholar

Wenk, H.R., Joswig, W., Tagai, T., Korekawa, M., and Smith, B.K. (1980) The average structure of An 62–66 labradorite. American Mineralogist, 65, 81–95.Search in Google Scholar

Wierman, C.T. (2018) Copper partitioning in mid-Miocene flood basalts from the Northern Great Basin (USA): Implications for Cu behavior in flood basalt provinces. Ph.D. dissertation, Kansas State University.Search in Google Scholar

Willets, K.A. and Van Duyne, R.P. (2007) Localized surface plasmon resonance spectroscopy and sensing. Annual Review of Physical Chemistry, 58, 267–297, https://doi.org/10.1146/annurev.physchem.58.032806.104607.Search in Google Scholar

Xu, X. and Cortie, M.B. (2006) Shape change and color gamut in gold nanorods, dumbbells, and dog bones. Advanced Functional Materials, 16, 2170–2176, https://doi.org/10.1002/adfm.200500878.Search in Google Scholar

Xu, H., Hill, T.R., Konishi, H., and Farfan, G. (2017) Protoenstatite: A new mineral in Oregon sunstones with “watermelon” colors. American Mineralogist, 102, 2146–2149, https://doi.org/10.2138/am-2017-6186.Search in Google Scholar

Zhang, W., Wang, C., Zhou, W., Yue, Z., and Liu, G. (2012) The analysis of Ag nanospheres and arrays LSPR phenomena based on DDA and FDTD method. Applied Mechanics and Materials, 110-116, 3860–3866.Search in Google Scholar

Zhou, Q., Wang, C., and Shen, A.H. (2022) Copper nanoparticles embedded in natural plagioclase mineral crystals: In situ formation and third-order nonlinearity. The Journal of Physical Chemistry C, 126, 387–395, https://doi.org/10.1021/acs.jpcc.1c09145.Search in Google Scholar

Zhu, J., Liu, G., Lil, X., Zheng, W., and Wang, B. (2018) Highly sensing characteristics of gold nanorings based on DDA analysis. In 2018 IEEE 27th International Symposium on Industrial Electronics, 976–981, Cairns, Australia.Search in Google Scholar

Zong, R.L., Zhou, J., Li, B., Fu, M., Shi, S.K., and Li, L.T. (2005) Optical properties of transparent copper nanorod and nanowire arrays embedded in anodic alumina oxide. The Journal of Chemical Physics, 123, 094710, https://doi.org/10.1063/1.2018642.Search in Google Scholar
Received: 2023-07-30
Accepted: 2024-05-09
Published Online: 2025-02-04
Published in Print: 2025-02-25

© 2025 Mineralogical Society of America

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https://doi.org/10.2138/am-2023-9141
Keywords for this article
Cu nanoparticles; Oregon sunstones; nano-inclusions; localized surface plasmon resonance; high-resolution transmission electron microscopy; plagioclase

Articles in the same Issue

  1. Gender in mineral names
  2. Role of impurities in the semiconducting properties of natural pyrite: Implications for the electrochemical accumulation of visible gold and formation of hydrothermal gold deposits
  3. Unraveling clay-mineral genesis and climate change on Earth and Mars using machine learning-based VNIR spectral modeling
  4. Characteristics of the distribution of minerals among the space groups
  5. Al3+ and H+ substitutions in TiO2 polymorphs: Structural and vibrational investigations
  6. Oriented triphylite rods in apatite from an LCT pegmatite in the Stankuvatske Li-ore deposit, Ukraine: Implications for Li mobility
  7. Quartz textures, trace elements, fluid inclusions, and in situ oxygen isotopes from Aktogai porphyry Cu deposit, Kazakhstan
  8. Cu nanoparticle geometry as the key to bicolor behavior in Oregon sunstones: An application of LSPR theory in nanomineralogy
  9. Gowerite, Ca[B5O8(OH)][B(OH)3]·3H2O: Revisiting the crystal structure and exploring its formation context
  10. Zhonghongite, Cu29(As, Sb)12S33, a new mineral from the high-sulfidation vein of Jiama porphyry system, Tibet, China
  11. Uramphite, (NH4)(UO2)(PO4)·3H2O, from the second world occurrence, Beshtau uranium deposit, Northern Caucasus, Russia: Crystal-structure refinement, infrared spectroscopy, and relation to uramarsite
  12. A simple method to create mineral mounts in thin section for teaching optical mineralogy
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