Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

# Seismic velocities of CaSiO3 perovskite can explain LLSVPs in Earth’s lower mantle

## Abstract

Seismology records the presence of various heterogeneities throughout the lower mantle1,2, but the origins of these signals—whether thermal or chemical—remain uncertain, and therefore much of the information that they hold about the nature of the deep Earth is obscured. Accurate interpretation of observed seismic velocities requires knowledge of the seismic properties of all of Earth’s possible mineral components. Calcium silicate (CaSiO3) perovskite is believed to be the third most abundant mineral throughout the lower mantle. Here we simultaneously measure the crystal structure and the shear-wave and compressional-wave velocities of samples of CaSiO3 perovskite, and provide direct constraints on the adiabatic bulk and shear moduli of this material. We observe that incorporation of titanium into CaSiO3 perovskite stabilizes the tetragonal structure at higher temperatures, and that the material’s shear modulus is substantially lower than is predicted by computations3,4,5 or thermodynamic datasets6. When combined with literature data and extrapolated, our results suggest that subducted oceanic crust will be visible as low-seismic-velocity anomalies throughout the lower mantle. In particular, we show that large low-shear-velocity provinces (LLSVPs) are consistent with moderate enrichment of recycled oceanic crust, and mid-mantle discontinuities can be explained by a tetragonal–cubic phase transition in Ti-bearing CaSiO3 perovskite.

## Access options

Rent or Buy article

from\$8.99

All prices are NET prices.

## Data availability

Raw data were collected at the European Synchrotron Radiation Facility in Grenoble and are available from https://doi.org/10.5285/6db95d87-365f-4018-abec-00e96e8fcf8d. Derived data from this study, which includes source data for Figs. 2 and 3 and Extended Data Figs. 1 and 5, are provided in the Supplementary Tables.

## Change history

• ### 23 August 2019

Owing to a technical error, this Letter was not published online on 14 August 2019, as originally stated, and was instead first published online on 15 August 2019. The Letter has been corrected online.

## References

1. 1.

Ritsema, J., Deuss, A., van Heijst, H. J. & Woodhouse, J. H. S40RTS: a degree-40 shear-velocity model for the mantle from new Rayleigh wave dispersion, teleseismic traveltime and normal-mode splitting function measurements. Geophys. J. Int. 184, 1223–1236 (2011).

2. 2.

Waszek, L., Schmerr, N. C. & Ballmer, M. D. Global observations of reflectors in the mid-mantle with implications for mantle structure and dynamics. Nat. Commun. 9, 385 (2018).

3. 3.

Stixrude, L., Lithgow-Bertelloni, C., Kiefer, B. & Fumagalli, P. Phase stability and shear softening in CaSiO3 perovskite at high pressure. Phys. Rev. B 75, 024108 (2007).

4. 4.

Kawai, K. & Tsuchiya, T. Small shear modulus of cubic CaSiO3 perovskite. Geophys. Res. Lett. 42, 2718–2726 (2015).

5. 5.

Li, L. et al. Elasticity of CaSiO3 perovskite at high pressure and high temperature. Phys. Earth Planet. Inter. 155, 249–259 (2006).

6. 6.

Stixrude, L. & Lithgow-Bertelloni, C. Thermodynamics of mantle minerals—II. Phase equilibria. Geophys. J. Int. 184, 1180–1213 (2011).

7. 7.

Ballmer, M. D., Schmerr, N. C., Nakagawa, T. & Ritsema, J. Compositional mantle layering revealed by slab stagnation at 1000-km depth. Sci. Adv. 1, e1500815 (2015).

8. 8.

Fukao, Y. & Obayashi, M. Subducted slabs stagnant above, penetrating through, and trapped below the 660 km discontinuity. J. Geophys. Res. 118, 5920–5938 (2013).

9. 9.

Stixrude, L. & Lithgow-Bertelloni, C. Geophysics of chemical heterogeneity in the mantle. Annu. Rev. Earth Planet. Sci. 40, 569–595 (2012).

10. 10.

Murakami, M., Ohishi, Y., Hirao, N. & Hirose, K. A perovskitic lower mantle inferred from high-pressure, high-temperature sound velocity data. Nature 485, 90–94 (2012).

11. 11.

Cottaar, S., Heister, T., Rose, I. & Unterborn, C. BurnMan: a lower mantle mineral physics toolkit. Geochem. Geophys. Geosyst. 15, 1164–1179 (2014).

12. 12.

Irifune, T. et al. Iron partitioning and density changes of pyrolite in Earth’s lower mantle. Science 327, 193–195 (2010).

13. 13.

Ricolleau, A. et al. Phase relations and equation of state of a natural MORB: implications for the density profile of subducted oceanic crust in the Earth’s lower mantle. J. Geophys. Res. 115, B08202 (2010).

14. 14.

Liu, L.-G. & Ringwood, A. E. Synthesis of a perovskite-type polymorph of CaSiO3. Earth Planet. Sci. Lett. 28, 209–211 (1975).

15. 15.

Dziewonski, A. M. & Anderson, D. L. Preliminary reference Earth model. Phys. Earth Planet. Inter. 25, 297–356 (1981).

16. 16.

Sinelnikov, Y. D., Chen, G. & Liebermann, R. C. Elasticity of CaTiO3-CaSiO3 perovskites. Phys. Chem. Miner. 25, 515–521 (1998).

17. 17.

Kudo, Y. et al. Sound velocity measurements of CaSiO3 perovskite to 133 GPa and implications for lowermost mantle seismic anomalies. Earth Planet. Sci. Lett. 349–350, 1–7 (2012).

18. 18.

Komabayashi, T., Hirose, K., Sata, N., Ohishi, Y. & Dubrovinsky, L. S. Phase transition in CaSiO3 perovskite. Earth Planet. Sci. Lett. 260, 564–569 (2007).

19. 19.

Chen, H. et al. Crystal structure of CaSiO3 perovskite at 28–62 GPa and 300 K under quasi-hydrostatic stress conditions. Am. Mineral. 103, 462–468 (2018).

20. 20.

Gréaux, S. et al. Sound velocity of CaSiO3 perovskite suggests the presence of basaltic crust in the Earth’s lower mantle. Nature 565, 218–221 (2019).

21. 21.

Thomson, A. R., Walter, M. J., Kohn, S. C. & Brooker, R. A. Slab melting as a barrier to deep carbon subduction. Nature 529, 76–79 (2016).

22. 22.

Li, B., Kung, J. & Liebermann, R. C. Modern techniques in measuring elasticity of Earth materials at high pressure and high temperature using ultrasonic interferometry in conjunction with synchrotron X-radiation in multi-anvil apparatus. Phys. Earth Planet. Inter. 143, 559–574 (2004).

23. 23.

Kurashina, T., Hirose, K., Ono, S., Sata, N. & Ohishi, Y. Phase transition in Al-bearing CaSiO3 perovskite: implications for seismic discontinuities in the lower mantle. Phys. Earth Planet. Inter. 145, 67–74 (2004).

24. 24.

Yashima, M. & Ali, R. Structural phase transition and octahedral tilting in the calcium titanate perovskite CaTiO3. Solid State Ion. 180, 120–126 (2009).

25. 25.

Salje, E. K. H. et al. Elastic excitations in BaTiO3 single crystals and ceramics: mobile domain boundaries and polar nanoregions observed by resonant ultrasonic spectroscopy. Phys. Rev. B 87, 014106 (2013).

26. 26.

Perks, N. J., Zhang, Z., Harrison, R. J. & Carpenter, M. A. Strain relaxation mechanisms of elastic softening and twin wall freezing associated with structural phase transitions in (Ca,Sr)TiO3 perovskites. J. Phys. Condens. Matter 26, 505402 (2014).

27. 27.

Liu, Z. et al. Elastic wave velocity of polycrystalline Mj80Py20 garnet to 21 GPa and 2,000 K. Phys. Chem. Miner. 42, 213–222 (2015).

28. 28.

Guennou, M., Bouvier, P., Kreisel, J. & Machon, D. Pressure-temperature phase diagram of SrTiO3 up to 53 GPa. Phys. Rev. B 81, 054115 (2010).

29. 29.

Stixrude, L. & Lithgow-Bertelloni, C. Thermodynamics of mantle minerals—I. Physical properties. Geophys. J. Int. 162, 610–632 (2005).

30. 30.

Garnero, E. J., McNamara, A. K. & Shim, S.-H. Continent-sized anomalous zones with low seismic velocity at the base of Earth’s mantle. Nat. Geosci. 9, 481–489 (2016).

31. 31.

Hofmann, A. W. Mantle geochemistry: the message from oceanic volcanism. Nature 385, 219–229 (1997).

32. 32.

Hirose, K., Fei, Y., Ma, Y. & Mao, H.-K. The fate of subducted basaltic crust in the Earth’s lower mantle. Nature 397, 53–56 (1999).

33. 33.

Deschamps, F., Cobden, L. & Tackley, P. J. The primitive nature of large low shear-wave velocity provinces. Earth Planet. Sci. Lett. 349–350, 198–208 (2012).

34. 34.

Guignard, J. & Crichton, W. A. The large volume press facility at ID06 beamline of the European synchrotron radiation facility as a high pressure-high temperature deformation apparatus. Rev. Sci. Instrum. 86, 085112 (2015).

35. 35.

Hammersley, A. P. FIT2D: An Introduction and Overview. Technical Report ESRF-97-HA-02T (ESRF, 1997).

36. 36.

Larson, A. C. & von Dreele, R. B. General Structure Analysis System (GSAS). Los Alamos National Laboratory Report LAUR 86–748 (LANL, 2004).

37. 37.

Dorogokupets, P. I., Dewaele, A. & Dewaele, A. Equations of state of MgO, Au, Pt, NaCl-B1, and NaCl-B2: internally consistent high-temperature pressure scales. High Press. Res. 27, 431–446 (2007).

38. 38.

Glazer, A. M. The classification of tilted octahedra in perovskites. Acta Crystallogr. B 28, 3384–3392 (1972).

39. 39.

Woodward, P. M. Octahedral tilting in perovskites. I. Geometrical considerations. Acta Crystallogr. A 53, 32–43 (1997).

40. 40.

Wood, I. G., Price, G. D., Street, J. N. & Knight, K. S. Equation of State and Structural Phase Transitions in CaTiO3 Perovskite. ISIS Experimental Report RB7844 (ISIS, 1997).

41. 41.

Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

42. 42.

Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

43. 43.

Perdew, J. P. et al. Restoring the density-gradient expansion for exchange in solids and surfaces. Phys. Rev. Lett. 100, 136406 (2008).

44. 44.

Togo, A. & Tanaka, I. First principles phonon calculations in materials science. Scr. Mater. 108, 1–5 (2015).

45. 45.

Shim, S.-H., Duffy, T. S. & Shen, G. The stability and P–V–T equation of state of CaSiO3 perovskite in the Earth’s lower mantle. J. Geophys. Res. 105, 25955–25968 (2000).

46. 46.

Sun, N. et al. Confirming a pyrolitic lower mantle using self-consistent pressure scales and new constraints on CaSiO3 perovskite. J. Geophys. Res. 121, 4876–4894 (2016).

47. 47.

Wang, Y., Weidner, D. J. & Guyot, F. Thermal equation of state of CaSiO3 perovskite. J. Geophys. Res. 101, 661–672 (1996).

48. 48.

Noguchi, M., Komabayashi, T., Hirose, K. & Ohishi, Y. High-temperature compression experiments of CaSiO3 perovskite to lowermost mantle conditions and its thermal equation of state. Phys. Chem. Miner. 40, 81–91 (2013).

49. 49.

Chust, T. C., Steinle-Neumann, G., Dolejš, D., Schuberth, B. S. A. & Bunge, H. P. MMA-EoS: a computational framework for mineralogical thermodynamics. J. Geophys. Res. 122, 9881–9920 (2017).

50. 50.

Brown, J. M. & Shankland, T. J. Thermodynamic parameters in the Earth as determined from seismic profiles. Geophys. J. R. Astron. Soc. 66, 579–596 (1981).

51. 51.

Zhang, Z., Stixrude, L. & Brodholt, J. Elastic properties of MgSiO3-perovskite under lower mantle conditions and the composition of the deep Earth. Earth Planet. Sci. Lett. 379, 1–12 (2013).

52. 52.

Wentzcovitch, R. M. et al. Anomalous compressibility of ferropericlase throughout the iron spin cross-over. Proc. Natl Acad. Sci. USA 106, 8447–8452 (2009).

53. 53.

Badro, J. et al. Electronic transitions in perovskite: possible non-convecting layers in the lower mantle. Science 305, 383–386 (2004).

54. 54.

Andrault, D., Fiquet, G., Guyot, F. & Hanfland, M. Pressure-induced Landau-type transition in stishovite. Science 282, 720–724 (1998).

55. 55.

Hernlund, J., Leinenweber, K., Locke, D. & Tyburczy, J. A. A numerical model for steady-state temperature distributions in solid-medium high-pressure cell assemblies. Am. Mineral. 91, 295–305 (2006).

56. 56.

Piskunov, S., Heifets, E., Eglitis, R. I. & Borstel, G. Bulk properties and electronic structure of SrTiO3, BaTiO3, PbTiO3 perovskites: an ab initio HF/DFT study. Comput. Mater. Sci. 29, 165–178 (2004).

57. 57.

Tadano, T. & Tsuneyuki, S. Self-consistent phonon calculations of lattice dynamical properties in cubic SrTiO3 with first-principles anharmonic force constants. Phys. Rev. B 92, 054301 (2015).

58. 58.

Hachemi, A., Hachemi, H., Ferhat-Hamida, A. & Louail, L. Elasticity of SrTiO3 perovskite under high pressure in cubic, tetragonal and orthorhombic phases. Phys. Scr. 82, 025602 (2010).

59. 59.

Caracas, R., Wentzcovitch, R., Price, G. D. & Brodholt, J. CaSiO3 perovskite at lower mantle pressures. Geophys. Res. Lett. 32, L06306 (2005).

60. 60.

Jung, D. Y. & Oganov, A. R. Ab initio study of the high-pressure behavior of CaSiO3 perovskite. Phys. Chem. Miner. 32, 146–153 (2005).

61. 61.

Mao, H. K. et al. Stability and equation of state of CaSiO3-perovskite to 134 GPa. J. Geophys. Res. 94, 17889–17894 (1989).

62. 62.

Yagi, T., Tsuchida, Y., Kusanagi, S. & Fukai, Y. Isothermal compression and stability of perovskite-type CaSiO3. Proc. Jpn. Acad. B 65, 129–132 (1989).

63. 63.

Tamai, H. & Yagi, T. High-pressure and high-temperature phase relations in CaSiO3 and CaMgSi2O6 and elasticity of perovskite-type CaSiO3. Phys. Earth Planet. Inter. 54, 370–377 (1989).

64. 64.

Tarrida, M. & Richet, P. Equation of state of CaSiO3 perovskite to 96 GPa. Geophys. Res. Lett. 16, 1351–1354 (1989).

## Acknowledgements

We acknowledge the support of NERC grants NE/PO17657/1 and NE/M00046X/1, and ESRF beamtime proposals ES-464 and ES-636. We thank G. Manthilake and D. Freitas for their assistance and for lending us ultrasonic equipment from Laboratoire Magmas et Volcans for use during the initial experiments of this study. Use of the Pixirad-8 detector was supported by the French Government via the ‘Investissements d’Avenir’ programme, under the reference ANR-10-AIRT-05.

## Author information

Authors

### Contributions

A.R.T. designed, performed and analysed the experiments, gathered data from the literature and wrote the manuscript. W.A.C. designed and developed the experimental procedure at ID06 of the ESRF. I.G.W. assisted with interpretation and refinement of diffraction data. J.P.B., D.P.D, W.A.C and N.C.S. helped perform experiments over two sessions at the ESRF. J.M.R.M. performed the computational simulations. S.A.H. assisted with data analysis. All authors contributed to the scientific discussion and preparation of the manuscript.

### Corresponding author

Correspondence to A. R. Thomson.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Peer review information Nature thanks Ian Jackson and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

## Extended data figures and tables

### Extended Data Fig. 1 Lattice and diffraction peak parameters for CaSiO3 and Ca[Si0.6Ti0.4]O3 perovskite.

ad, Refined lattice parameters and pseudo-cubic unit cell volumes from Ca[Si0.6Ti0.4]O3 (a, c) and CaSiO3 (b, d) plotted as a function of experimental temperature with 2σ uncertainties. e, Full-width at half-maximum (FWHM) of diffraction peaks (see key) of the CaSiO3 perovskite sample, normalized to the FWHM at high temperature, measured at 100 K intervals in a separate experiment to that in Fig. 2.

### Extended Data Fig. 2 X-ray diffraction patterns from CaSiO3 perovskite.

Shown are stacked diffraction patterns of CaSiO3 perovskite; each panel shows data at 300 K, 373 K and 473 K (see key in a). a, Full patterns; b, c, patterns limited in the 2θ range to allow indication of weak superlattice peaks. The positions of the diffraction peaks from the Ca-Pv sample, MgO, NaCl and Au are indicated by markers—other small peaks are from boron epoxy and/or furnace components. Cubic Ca-Pv peaks are labelled with indices, hkl, in bold. The diffraction patterns reveal the appearance of small superlattice reflections at T = 373 K and 300 K at 2θ values of about 6.1°, 8.05°, 12.1° and 13.2° (we note there is believed to be an additional superlattice reflection obscured at 2θ = 10.5°) labelled with hkl indexed on the tetragonal (I4/mcm) unit cell and marked with gold stars.

### Extended Data Fig. 3 Refined X-ray diffraction patterns from Ca[Si0.6Ti0.4]O3 perovskite.

ac, Rietveld refinements of Ca[Si0.6Ti0.4]O3 samples: a, in P21/c with LaB6 calibrant, at 300 K and ambient pressure; b, in the tetragonal I4/m structure (with other cell components) at 890 K and high pressure (about 12 GPa); and c, in $$Fm\bar{3}m$$ at 1,336 K and high pressure (12 GPa). In each panel, the black dots are the collected data, the blue curve the model pattern and the green curve the residual. The coloured tick-marks indicate the positions of diffraction peaks of each phase.

### Extended Data Fig. 4 X-ray diffraction patterns from Ca[Si0.6Ti0.4]O3 perovskite.

a, Complete diffraction pattern of the Ca[Si0.6Ti0.4]O3 sample as a function of temperature at about 12 GPa, with diffraction intensity indicted by colour scaling. bh, Magnified panels from a focusing on the temperature evolution of the 311, 222, 400, 422, 440, 620 and 444 diffraction peaks (bh, respectively; indexed using a cubic lattice with a ≈ 7.3 Å), demonstrating the change in thermal expansivity between cubic and tetragonal/monoclinic structures, and allowing visual identification of the observed phase transitions.

### Extended Data Fig. 5 Phase diagram of calcium perovskite throughout the mantle from ab initio simulations and experiments.

Shown is the cubic–tetragonal transition extrapolated throughout the mantle based on ab initio (solid circles) and experimental (triangles) constraints from this study. Vertical error bars (1σ) and the grey envelope (80% confidence interval) represent the uncertainty in computational results from this study. A 1,500 K mantle adiabat and cold slab temperature profile are plotted as red curves, with dashed red arrows indicating the warming occurring during slab stagnation at 700–1,000 km depth. Results from previous experimental18,23 and computational3 studies are plotted as open symbols and grey curves, respectively.

### Extended Data Fig. 6 Equations of state for CaSiO3 perovskite.

a, PV EoS for tetragonal CaSiO3 at 300 K, fitted to data from this study only (purple line) and combined with data from previous studies (thick black curve). Only data with large symbols, those that used pressure transmitting media, have been included in fitting the EoS. All small symbols are from experiments that did not employ a pressure-transmitting medium so have been excluded as volumes are expected to be affected by residual sample stress. Additionally, data from Wang et al.47 were excluded as they used energy dispersive diffraction in the large volume press, which can be subject to larger uncertainties in volume. Error bars represent pressure and volume uncertainties as reported in previous studies. Computational EoS for tetragonal Ca-Pv are plotted as dashed curves for comparison3,17,19,45,47,59,60,61,62,63,64. b, PVT EoS for cubic CaSiO3 perovskite at 298 K and along a 1,600 K adiabat fitted to data from this and previous studies. Small, partially transparent symbols are literature data that were not included in the fitting, either due to falling below the calculated slope of the cubic–tetragonal transition (Methods) or due to concerns about data accuracy. The inset histogram shows the, approximately normal, distribution for the residuals for the fitted data compared with the best-fit model, demonstrating the lack of outliers45,46,47,48.

### Extended Data Fig. 7 Bulk sound velocity and bulk modulus of CaSiO3 perovskite.

a, Bulk sound velocity of Ca-Pv predicted from the EoS in this study along a 1,600 K mantle adiabat and at 300 K, compared with results from previous computational studies on a 1,600 K adiabat4,5,6, a fit to previously published PVT diffraction data, and PREM15. b, The adiabatic bulk modulus of CaSiO3 perovskite calculated at 300 K and along a 1,600 K mantle adiabat using the finite strain model from this study, compared with thermodynamic results in Stixrude et al.6 and previous high-temperature computational studies4,5.

### Extended Data Fig. 8 Exemplar radiographic image, ultrasonic data and schematic of the experimental cell design.

a, Example of synchrotron radiographic image in plan view used to measure sample length in a Ca[Si0.6Ti0.4]O3 sample. b, Ultrasonic signals from the ‘runa’ experiment on a CaSiO3 sample. c, Cross-section of the experimental assembly (to scale) used in ultrasonic experiments throughout this study.

### Extended Data Fig. 9 Comparison of bulk sound velocity from diffraction and ultrasonic measurements.

Shown is a comparison of bulk sound velocity calculated from PVT EoSs, fitted to literature diffraction data (solid curves) with 2σ uncertainties shown by shaded regions, and only to that reported by Gréaux et al.20 (dashed curves), with bulk sound velocities calculated from ultrasonic measurements via vbulk = (vP2 − 4/3vS2)0.5 for data from Gréaux et al.20 (squares) and this study (circles). All curves and symbols are coloured for temperature (colour scale at right).

## Supplementary information

### Supplementary Tables

Supplementary Tables 1–7

## Rights and permissions

Reprints and Permissions

Thomson, A.R., Crichton, W.A., Brodholt, J.P. et al. Seismic velocities of CaSiO3 perovskite can explain LLSVPs in Earth’s lower mantle. Nature 572, 643–647 (2019). https://doi.org/10.1038/s41586-019-1483-x

• Accepted:

• Published:

• Issue Date:

• ### Constraints on the composition and temperature of LLSVPs from seismic properties of lower mantle minerals

• Kenny Vilella
• , Thomas Bodin
• , Charles-Edouard Boukaré
• , Frédéric Deschamps
• , James Badro
• , Maxim D. Ballmer
•  & Yang Li

Earth and Planetary Science Letters (2021)

• ### Structural changes in aluminosilicate glasses up to 164 GPa and the role of alkali, alkaline earth cations and alumina in the densification mechanism

• Marija Krstulović
• , Angelika D. Rosa
• , Nicole Biedermann
• , Tetsuo Irifune
•  & Max Wilke

Chemical Geology (2021)

• ### The effect of iron on the sound velocities of δ-AlOOH up to 135 ​GPa

• Xiaowan Su
• , Chaoshuai Zhao
• , Chaojia Lv
• , Yukai Zhuang
• , Nilesh Salke
• , Liangxu Xu
• , Hu Tang
• , Huiyang Gou
• , Xiaohui Yu
• , Qiang Sun
•  & Jin Liu

Geoscience Frontiers (2021)

• ### Origin, properties, and structure of breyite: The second most abundant mineral inclusion in super-deep diamonds

• Frank E. Brenker
• , Fabrizio Nestola
• , Lion Brenker
• , Luca Peruzzo
•  & Jeffrey W. Harris

American Mineralogist (2021)

• ### High-pressure silica phase transitions: Implications for deep mantle dynamics and silica crystallization in the protocore

• Pratik Kr. Das
• , Chris E. Mohn
• , John P. Brodholt
•  & Reidar G. Trønnes

American Mineralogist (2020)