Skip to main content

Thank you for visiting 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.

  • Letter
  • Published:

Blue boron-bearing diamonds from Earth’s lower mantle

Matters Arising to this article was published on 12 June 2019


Geological pathways for the recycling of Earth’s surface materials into the mantle are both driven and obscured by plate tectonics1,2,3. Gauging the extent of this recycling is difficult because subducted crustal components are often released at relatively shallow depths, below arc volcanoes4,5,6,7. The conspicuous existence of blue boron-bearing diamonds (type IIb)8,9 reveals that boron, an element abundant in the continental and oceanic crust, is present in certain diamond-forming fluids at mantle depths. However, both the provenance of the boron and the geological setting of diamond crystallization were unknown. Here we show that boron-bearing diamonds carry previously unrecognized mineral assemblages whose high-pressure precursors were stable in metamorphosed oceanic lithospheric slabs at depths reaching the lower mantle. We propose that some of the boron in seawater-serpentinized oceanic lithosphere is subducted into the deep mantle, where it is released with hydrous fluids that enable diamond growth10. Type IIb diamonds are thus among the deepest diamonds ever found and indicate a viable pathway for the deep-mantle recycling of crustal elements.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Selected Raman spectra of inclusions in type IIb diamonds.
Fig. 2: Inclusions jacketed by thin films of fluid CH4 and H2, revealed by Raman spectroscopy.
Fig. 3: Formation of type IIb diamond.

Similar content being viewed by others


  1. Kendrick, M. A. et al. Seawater cycled throughout Earth’s mantle in partially serpentinized lithosphere. Nat. Geosci. 10, 222–228 (2017).

    Article  ADS  CAS  Google Scholar 

  2. Tackley, P. J. Mantle convection and plate tectonics: toward an integrated physical and chemical theory. Science 288, 2002–2007 (2000).

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  4. Leeman, W. P., Tonarini, S. & Turner, S. Boron isotope variations in Tonga-Kermadec-New Zealand arc lavas: implications for the origin of subduction components and mantle influences. Geochem. Geophys. Geosyst. 18, 1126–1162 (2017).

    Article  ADS  CAS  Google Scholar 

  5. Deschamps, F., Godard, M., Guillot, S. & Hattori, K. Geochemistry of subduction zone serpentinites: A review. Lithos 178, 96–127 (2013).

    Article  ADS  CAS  Google Scholar 

  6. Plank, T. & Langmuir, C. H. The chemical composition of subducting sediment and its consequences for the crust and mantle. Chem. Geol. 145, 325–394 (1998).

    Article  ADS  CAS  Google Scholar 

  7. Konrad-Schmolke, M., Halama, R. & Manea, V. C. Slab mantle dehydrates beneath Kamchatka—yet recycles water into the deep mantle. Geochem. Geophys. Geosyst. 17, 2987–3007 (2016).

    Article  ADS  Google Scholar 

  8. Gaillou, E., Post, J. E., Rost, D. & Butler, J. E. Boron in natural type IIb blue diamonds: chemical and spectroscopic measurements. Am. Mineral. 97, 1–18 (2012).

    Article  ADS  CAS  Google Scholar 

  9. King, J. M. et al. Characterizing natural-color type IIb blue diamonds. Gems Gemol. 34, 246–268 (1998).

    Article  Google Scholar 

  10. Harte, B. Diamond formation in the deep mantle: the record of mineral inclusions and their distribution in relation to mantle dehydration zones. Mineral. Mag. 74, 189–215 (2010).

    Article  CAS  Google Scholar 

  11. Grew, E. S. Boron: from cosmic scarcity to 300 minerals. Elements 13, 225–229 (2017).

    CAS  Google Scholar 

  12. Wu, F. Y. et al. In situ U-Pb age determination and Sr-Nd isotopic analysis of perovskite from the Premier (Cullinan) kimberlite, South Africa. Chem. Geol. 353, 83–95 (2013).

    Article  ADS  CAS  Google Scholar 

  13. Skinner, E. & Truswell, J. in The Geology of South Africa (eds Johnson, M. R. et al.) 651–659 (Geological Society of South Africa, Johannesburg, 2006).

  14. Walter, M. J. et al. Deep mantle cycling of oceanic crust: evidence from diamonds and their mineral inclusions. Science 334, 54–57 (2011).

    Article  ADS  CAS  Google Scholar 

  15. Stachel, T., Harris, J. W., Brey, G. P. & Joswig, W. Kankan diamonds (Guinea) II: lower mantle inclusion parageneses. Contrib. Mineral. Petrol. 140, 16–27 (2000).

    Article  ADS  CAS  Google Scholar 

  16. Thomson, A. et al. Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions. Contrib. Mineral. Petrol. 168, 1081 (2014).

    Article  ADS  Google Scholar 

  17. Harte, B. & Hudson, N. C. F. In Proc. 10th International Kimberlite Conference Vol. 1 (eds Pearson, D. G. et al.) 235–253 (Springer, New Delhi, 2013).

  18. Nestola, F. et al. CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle. Nature 555, 237–241 (2018).

    Article  ADS  CAS  Google Scholar 

  19. Brenker, F. E. et al. Detection of a Ca-rich lithology in the Earth’s deep (> 300 km) convecting mantle. Earth Planet. Sci. Lett. 236, 579–587 (2005).

    Article  ADS  CAS  Google Scholar 

  20. Anzolini, C. et al. Depth of formation of CaSiO3-walstromite included in super-deep diamonds. Lithos 265, 138–147 (2016).

    Article  ADS  CAS  Google Scholar 

  21. Smith, E. M. et al. Large gem diamonds from metallic liquid in Earth’s deep mantle. Science 354, 1403–1405 (2016).

    Article  ADS  CAS  Google Scholar 

  22. Anzolini, C. et al. Depth of formation of super-deep diamonds: Raman barometry of CaSiO3-walstromite inclusions. Am. Mineral. 103, 69–74 (2018).

    Article  ADS  Google Scholar 

  23. Angel, R. J., Mazzucchelli, M. L., Alvaro, M. & Nestola, F. EosFit-Pinc: a simple GUI for host-inclusion elastic thermobarometry. Am. Mineral. 102, 1957–1960 (2017).

    Article  ADS  Google Scholar 

  24. Hanley, P. L., Kiflawi, I. & Lang, A. R. On topographically identifiable sources of cathodoluminescence in natural diamonds. Phil. Trans. R. Soc. Lond. A 284, 329–368 (1977).

    Article  ADS  CAS  Google Scholar 

  25. Stachel, T., Harris, J., Aulbach, S. & Deines, P. Kankan diamonds (Guinea) III: d13C and nitrogen characteristics of deep diamonds. Contrib. Mineral. Petrol. 142, 465–475 (2002).

    Article  ADS  CAS  Google Scholar 

  26. Milledge, H. J. et al. Carbon isotopic variation in spectral type II diamonds. Nature 303, 791–792 (1983).

    Article  ADS  CAS  Google Scholar 

  27. Pabst, S. et al. Evidence for boron incorporation into the serpentine crystal structure. Am. Mineral. 96, 1112–1119 (2011).

    Article  ADS  CAS  Google Scholar 

  28. Ohtani, E., Litasov, K., Hosoya, T., Kubo, T. & Kondo, T. Water transport into the deep mantle and formation of a hydrous transition zone. Phys. Earth Planet. Inter. 143–144, 255–269 (2004).

    Article  ADS  Google Scholar 

  29. Pearson, D. G. et al. Hydrous mantle transition zone indicated by ringwoodite included within diamond. Nature 507, 221–224 (2014).

    Article  ADS  CAS  Google Scholar 

  30. Nestola, F. et al. Tetragonal Almandine-Pyrope Phase, TAPP: finally a name for it, the new mineral jeffbenite. Mineral. Mag. 80, 1219–1232 (2016).

    Article  CAS  Google Scholar 

  31. Liu, J., Li, J. & Ikuta, D. Elastic softening in Fe7C3 with implications for Earth’s deep carbon reservoirs. J. Geophys. Res. Solid Earth 121, 1514–1524 (2016).

    Article  ADS  CAS  Google Scholar 

  32. Howell, D., Wood, I. G., Nestola, F., Nimis, P. & Nasdala, L. Inclusions under remnant pressure in diamond: a multi-technique approach. Eur. J. Mineral. 24, 563–573 (2012).

    Article  ADS  CAS  Google Scholar 

  33. Nestola, F. et al. First crystal-structure determination of olivine in diamond: composition and implications for provenance in the Earth’s mantle. Earth Planet. Sci. Lett. 305, 249–255 (2011).

    Article  ADS  CAS  Google Scholar 

  34. Mazzucchelli, M. L. et al. Elastic geothermobarometry: corrections for the geometry of the host-inclusion system. Geology 46, 231–234 (2018).

    Article  ADS  CAS  Google Scholar 

  35. Angel, R. J., Alvaro, M., Miletich, R. & Nestola, F. A simple and generalised P–T–V EoS for continuous phase transitions, implemented in EosFit and applied to quartz. Contrib. Mineral. Petrol. 172, 29 (2017).

    Article  ADS  Google Scholar 

  36. Gonzalez-Platas, J., Alvaro, M., Nestola, F. & Angel, R. EosFit7-GUI: a new graphical user interface for equation of state calculations, analyses and teaching. J. Appl. Cryst. 49, 1377–1382 (2016).

    Article  CAS  Google Scholar 

  37. Angel, R., Alvaro, M., Nestola, F. & Mazzucchelli, M. Diamond thermoelastic properties and implications for determining the pressure of formation of diamond-inclusion systems. Russ. Geol. Geophys. 56, 211–220 (2015).

    Article  Google Scholar 

  38. Angel, R., Nimis, P., Mazzucchelli, M., Alvaro, M. & Nestola, F. How large are departures from lithostatic pressure? Constraints from host–inclusion elasticity. J. Metamorph. Geol. 33, 801–813 (2015).

    Article  ADS  Google Scholar 

  39. Angel, R. J., Alvaro, M. & Gonzalez-Platas, J. EosFit7c and a Fortran module (library) for equation of state calculations. Z. Kristallogr. Cryst. Mater. 229, 405–419 (2014).

    Article  CAS  Google Scholar 

  40. Angel, R. J., Mazzucchelli, M. L., Alvaro, M., Nimis, P. & Nestola, F. Geobarometry from host-inclusion systems: the role of elastic relaxation. Am. Mineral. 99, 2146–2149 (2014).

    Article  ADS  Google Scholar 

  41. Hemley, R. J. in High-Pressure Research in Mineral Physics Vol. 39 (eds Manghnani, M. H. & Syono, Y.) 347–359 (American Geophysical Union, Washington DC, 1987).

  42. Sobolev, N. V. et al. Fossilized high pressure from the Earth’s deep interior: the coesite-in-diamond barometer. Proc. Natl Acad. Sci. USA 97, 11875–11879 (2000).

    Article  ADS  CAS  Google Scholar 

  43. Smith, E. M., Kopylova, M. G., Frezzotti, M. L. & Afanasiev, V. P. Fluid inclusions in Ebelyakh diamonds: evidence of CO2 liberation in eclogite and the effect of H2O on diamond habit. Lithos 216-217, 106–117 (2015).

    Article  ADS  CAS  Google Scholar 

  44. Smith, E. M., Vendrell, C. & Johnson, P. Coesite inclusions with filaments in diamond. Gems Gemol. 52, 410–412 (2016).

    Google Scholar 

  45. D’Ippolito, V., Andreozzi, G. B., Bersani, D. & Lottici, P. P. Raman fingerprint of chromate, aluminate and ferrite spinels. J. Raman Spectrosc. 46, 1255–1264 (2015).

    Article  ADS  Google Scholar 

Download references


This research was supported by a GIA Liddicoat Postdoctoral Research Fellowship to E.M.S. Support to S.B.S. and F.N. was provided by the Deep Carbon Observatory (DCO). The European Research Council supported F.N. (INDIMEDEA, number 307322). Sincere thanks to K. S. Moe, T. Moses, M. Breeding, U. D’Haenens-Johansson, P. Johnson, K. Smit, J. Liao, S. Persaud, E. Myagkaya, A. Balter and B. Torres for analytical/logistical assistance, to N. Renfro for the micrograph of Fig. 1a, to Ascot Diamonds for lending rough samples and to M. Alvaro for discussions about geobarometry.

Reviewer information

Nature thanks E. Gaillou and T. Stachel for their contribution to the peer review of this work.

Author information

Authors and Affiliations



E.M.S. led the research, characterized the samples, conducted Raman analyses, interpreted results and wrote the initial manuscript. S.B.S. and S.H.R. contributed scientific interpretations and substantive manuscript writing. F.N. conducted X-ray diffraction and assisted with geobarometry. E.S.B. provided support for electron microprobe analysis. J.W. conducted mass spectroscopy for carbon. W.W. helped guide the project and ensured access to samples and analytical resources.

Corresponding author

Correspondence to Evan M. Smith.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

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

Extended data figures and tables

Extended Data Fig. 1 Suite of 46 type IIb diamonds studied.

Images are not to scale. Refer to noted dimensions (max diam., maximum diameter).

Extended Data Fig. 2 Mineralogy of mantle rocks with peridotitic and basaltic bulk composition as a function of depth.

Numbers in boxes denote the number of diamonds observed with inclusions of the given phase, and blue shading in the boxes indicates that a thin fluid CH4 ± H2 jacket was found with the phase. We note that the division of samples between the left and right panel is for illustrative purposes, and in reality some samples (for example, with Ca-Pv alone) are not firmly categorized. See Extended Data Table 1 for a breakdown of inclusions by sample. Adapted from ref. 17.

Extended Data Fig. 3 Multiphase inclusion interpreted as former low-Ca, high-Na majoritic garnet.

a, Optical microscope image of the inclusion, exposed on a polished facet of sample 880000037816. b, Secondary-electron image of the same inclusion, grooved with nearly horizontal polishing lines. c, d, EDS spectra of the two phases, consistent with their Raman identification as jeffbenite and NaAl-pyroxene (monoclinic, with composition between enstatite and jadeite). High Na content suggests a metabasaltic paragenesis, while low Ca content may reflect Ca partitioning into coexisting Ca-Pv at the base of the mantle transition zone or the uppermost lower mantle.

Extended Data Fig. 4 Diamond sample 110208425476.

a, Optical microscope image of the whole diamond, showing multiple dark inclusions of ferropericlase. b, Polishing down the table facet slightly exposed this group of four ferropericlase inclusions, shown here in an electron backscatter image. The smeared texture on the largest inclusion is a small amount of iron inadvertently deposited on the surface during polishing on a conventional cast iron scaife. c, Cathodoluminescence image of the whole diamond, revealing a complex dislocation network pattern, with interspersed healed fractures, that records a combination of both plastic and brittle deformation.

Extended Data Fig. 5 Multiphase Fe–S–C–O metallic inclusion in sample 110208245246 (inclusion B).

a, Optical microscope image of inclusion B, while still contained within the diamond host. b, Electron backscatter image of the inclusion, after polishing to expose a cross-section through it. The three main phases are colour-coded in the right panel. c, X-ray spectra obtained with EDS, showing the qualitative elemental composition of each of the three phases. Carbon is present in all spectra owing to the diamond host, diamond particles embedded in the polished surface (black specks, especially in the sulphide phase), as well as the carbon inherent to the Fe-carbide phase. d, X-ray elemental maps obtained with EDS, showing the spatial variation in signal in the region of Fe, S and O peaks (Kα1). Sulphur delineates the Fe-sulphide phase. Oxygen marks the Fe-oxide phase, while also showing the variable oxidation/tarnish layer on the sulphide portion of the inclusion.

Extended Data Fig. 6 Two inclusions exhibiting a large pressure-induced shift in Raman features.

a, CaSiO3 walstromite (thought to be former Ca-Pv) in sample 110203744064, inclusion A, with the three main peaks shifted to higher wavenumbers compared to a zero-pressure reference spectrum. This inclusion also contains CH4. b, Coesite (SiO2, thought to be former stishovite) in sample 890000180198. The inclusion analysed (circled) is about 2 µm wide and lies in a planar lobate healed crack, along with other related ‘satellite’ inclusions that presumably surrounded a nucleus coesite inclusion that was polished away when this diamond was facetted. Neighbouring coesite inclusions in b also have high, but variable, remnant pressures, as reflected by the Raman spectra. Reference spectra are from ref. 19 and RRUFF-X050094, and zero-pressure reference peak positions are taken from refs22,41.

Extended Data Fig. 7 Dislocation network pattern in sample 110208245246, as seen in panchromatic cathodoluminescence.

Each of the bright web-like lines are made up of many dislocations, and these cathodoluminescent boundaries surround darker, low-strain domains. The dark curved feature on the right of the centre is a crack (not healed).

Extended Data Table 1 Suite of 46 type IIb diamond samples and inclusion summary

Supplementary information

Supplementary Table 1

Electron microprobe results for exposed ferropericlase inclusions in sample 110208425476 (also see Extended Data Fig. 5)

Supplementary Table 2

Electron microprobe analyses for a multiphase Fe-S-C-O inclusion in sample 110208245246.

Supplementary Table 3

Carbon isotopic compositions for 3 Type IIb diamond samples (110208425476, 110208425246, DVBT).

Source Data for Figure 1

Source Data for Figure 2

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Smith, E.M., Shirey, S.B., Richardson, S.H. et al. Blue boron-bearing diamonds from Earth’s lower mantle. Nature 560, 84–87 (2018).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing