I obtained my Master's degree in Geology in 2003 from the University of Clermont-Ferrand (France) and my Ph.D. in Materials Science in 2006 from the Institut des Matériaux Jean Rouxel (IMN) Nantes (France). From 2006 to 2010, I was a postdoctoral research fellow in the Department of Mineral Sciences at the Smithsonian Institution and then I held a combined postdoctoral research fellowship with both the Smithsonian and the Carnegie Institution (Department of Terrestrial Magnetism) until the end of 2011. My research focuses on gem materials, especially opals and diamonds.
The Gem & Mineral Council provides a varied schedule of activities including exciting field trips, educational lectures, and exclusive social events. The Council is also vital in providing support for the Museum's acquisition, exhibition, and research efforts in the field of gems and minerals. To learn more about The Gem & Mineral Council and how you can become a member, visit The Gem & Mineral Council webpage.
NHM's gem and mineral collection of about 150,000 specimens is the most significant in the country, west of the Smithsonian. See More
The 6,000-square-foot Gem and Mineral Hall was opened in May of 1978. Another 1,500 square-foot gallery titled Gemstones and their Origins was added in May of 1985. Together they comprise one of the finest exhibits of gems and minerals in the world. In 1989, Los Angeles magazine rated it as the finest permanent museum exhibition of any kind in the Los Angeles area.
By Eloïse Gaillou
About my research... and general information on diamonds.
I-THE COLOR OF DIAMONDS.
Fig. 1: Rose cut and cuboid rough diamonds, showing a variety of colors.
Diamonds don't only come in "white" (or properly speaking: colorless). Their color variety spans the full spectrum range: from brown (the most common color for diamonds), to black, to milky, to yellow, to the rarest green, orange, pink, purple, red and blue (see Fig. 1). The cause of the coloration is known to be due to impurities and / or imperfections:
- The color of natural BROWN diamonds is still under investigation, but this color might be due to the presence of extended defects, related to clusters of vacancies (or tiny "holes" inside the diamond structure! e.g. Fisher et al., 2009). These vacancy clusters might be formed during an event of plastic deformation: inside the Earth's mantle, the pressure conditions are extremely high, and stress can be applied to the minerals that are contained in the mantle. As underneath high pressure combined with high temperature, the minerals won't necessary break, but will be deformed. The deformation involves some re-arrangement of the atomic structure, creating "holes" or vacancies, which can migrate with time and temperature to find other vacancies inside the diamonds, forming the clusters. For the time being, this process of formation is still speculative.
- The YELLOW color of most yellow diamonds is due to nitrogen-related impurities for most (the N3 center, isolated nitrogen -type Ib-, e.g. Fritsch, 1998).
- The BLUE color for most blue diamonds is related to the presence of boron (e.g. Fritsch, 1998; King et al., 1998, Gaillou et al., 2012), even in very small quantity (usually less than one boron atom per million of carbon atoms is enough to give rise to a blue color). Some scientific details are given below.
- The GREY to GRAYISH-BLUE to VIOLET colors typical of some diamonds from the deposit of Argyle, in Australia is most likely associated with the presence of hydrogen impurities (Fristch & Scarratt, 1992; Van Der Bogert et al., 2009; Goss et al., 2011).
I-1.THE NATURE OF THE PINK COLOR IN NATURAL DIAMONDS.
The origin of the pink color, which sometimes has a purple hue or a dark tone (sometimes described as “red”), is still not completely understood. Plastic deformation is known to play an important role in the development of pink lamellae or “graining” within colorless diamonds (Fig. 1). The color is the result of a broad absorption band centered at about 550-560 nm that absorbs most of the visible spectrum except for the red. Thus far, the cause of this absorption feature is unknown, and unfortunately, the center, or other defect that is responsible for the absorption does not seem to be active in any other spectroscopic mode.
In our study (Gaillou et al., 2010), we recognized that there are two distinct groups of type Ia (that is, containing nitrogen impurities in aggregate states) natural pink diamonds:
- group 1: Natural pink diamonds from Argyle in Australia and from Santa Elena in Venezuela. For these diamonds, the pink color is widespread, forming wavy bands inside a colorless diamond (see Fig. 2 & 3).
Fig. 2: A pink diamond from Argyle, Australia.
Fig. 3: Slice of pink diamond from Argyle, polished perpendicularly to the pink graining. Wavy bands of colorless/pink areas are visible.
- group 2: Natural pink diamonds from other localities (including: Canada, Russia, Siberia, South Africa and Tanzania). For these diamonds, the pink color is restricted to thin pink lamellae in a colorless diamond (see Fig. 3).
Fig. 4: Rough diamond from Brazil.
Fig. 5: Slice of pink diamond (group 2).
These 2 groups present spectroscopic features that are different (by Raman spectroscopy, cathodoluminescence, photoluminescence); they are extensively described in Gaillou et al. (2010). Examples of cathodoluminescence imagery are given in Fig. 6 & 7. In all cases though, all the defects involved nitrogen aggregates associated with vacancies (such as the new 405.5 nm center and the well known H3 center).
Fig. 6: Cathodoluminescence picture of a pink Argyle diamond (group 1). In blue: growth sectors (N3 centers), in green: H3 centers describing a "fish-scale" pattern.
Fig. 7: Cathodoluminescence image of a pink diamond (group 2). The pink lamellae emit a green CL (H3 centers + less intense 405.5 nm center), the colorless diamond emit a blue luminescence (from the "blue band", also called "band A").
For the second group of diamond, it was recently suggested (Mineeva et al., 2009) and then confirmed (Gaillou et al., 2010; Titkov et al., 2012) that plastic deformation and subsequent annealing is manifested by the presence of pairs of twin planes. No similar studies have been conducted on group 1 diamonds so far, so we can only speculate that similar processes happen for group 2 diamonds.
We therefore proposed that to accommodate deformation, mechanical twinning takes place, which also creates vacancies. With time and the high temperature existing in the Earth's mantle, the vacancies created at the twins can move to the next nitrogen aggregates (here, most likely A-aggregates) to form the new 405.5 nm center, the H3 center, and the center responsible for the pink color.
To learn more about this, dowload the pdf of the article.
I-2. BORON CONTENT IN NATURAL BLUE DIAMONDS.
Fig. 8: A natural blue diamond.
Boron is known to be the coloring agent in blue diamonds (Fig. 8), as this element causes a strong absorption in the infrared, tailing off in the visible range. However, the concentration of boron is reported to be very low (less than 0.5 ppm) in natural diamonds, and therefore difficult to measure. That is probably why most of the works conducted on boron in diamonds have been done on synthetic, boron doped diamonds, which can contain boron up to about 1,000 ppm. An indirect way to measure boron is to use the intensity of some absorption lines in the infrared to calculate the boron concentration. But this method does not take into account the boron that might interact with other possible impurities (such as nitrogen or hydrogen) and that will be inactive in the infrared: only the so-called uncompensated boron is visible. Our work consists in comparing the different methods of measuring boron in natural blue diamonds, and to develop a new method of direct chemical analyses of the total boron content by Time-of-Flight SIMS (ToF-SIMS; Fig. 9). This method is nearly non-destructive, and we were able to conduct the analyses on extremely valuable samples, such as the HOPE, the BLUE HEART and the CULLINAN blue diamonds.
Fig. 9: ToF SIMS of the Smithsonian Institution, with which Boron measurements were conducted.
Fig. 10: Phosphorescence spectrum for a typical blue diamond: The emission is dominated by a short blue band at 500nm, with a less intense red 660 nm band. In the case of the Hope and Wittelsbach diamonds, the red band dominates.
I-3. DIAMONDS IN THE NATIONAL GEM COLLECTION.
The National Museum of Natural History gave me a unique opportunity during my postdoc position at the Smithsonian to look at incredible gems and minerals. Part of the work I have been conducted involves the characterization of some of the diamonds of the National Gem Collection, such as the Napoléon Diamond Necklace, or diamonds that were temporary on loan to the Museum, such as the Wittelsbach-Graff diamond.
II- THE ORIGIN OF DIAMONDS
III- PUBLICATION LIST
III-1. PEER REVIEWED PUBLICATIONS
Gaillou E., Post J.E., Butler J.E. (2012)Boron in natural type IIb blue diamonds: chemical and spectroscopic measurements. American Mineralogist, Vol. 97, No 1, 1-18.
Gaillou E., Fritsch E., Massuyeau F. (2012) Luminescence of gem opals: a review of intrinsic and extrinsic emission. Australian Gemmologist, Vol. 24, No 8, pp. 200-201.
Rondeau B., Cenki-Tok B., Fritsch E., Mazzero F., Gauthier J.-P., Bodeur Y., Bekele E., Gaillou E., Ayalew D. (2011) Geochemical and petrological characterization of gem opals from Wegel Tena, Wollo, Ethiopia: opal formation in an oligocene soil. Geochemistry: Exploration, Environment, Analysis, In Press.
Walter M.J., Kohn S.C., Araujo D., Bulanova G.P., Smith C.B., Gaillou E., Wang J., Steele A., Shirey S.B. (2011)Deep mantle cycling of oceanic crust: evidence from diamonds and their mineral inclusions. Science, vol. 334, No 6052, pp. 54-57.
Gaillou E., Post J.E., Wang W., King J.M., Moses T.M., Butler J.E. (2010) More on the Wittelsbach-Graff and Hope diamonds. Gems & Gemology, vol. 46, No 3, pp. S1, S4.
Gaillou E., Post J.E., Bassim N., Fries M., Rose T., Stroud R., Butler J.E. (2010) Spectroscopic and microscopic characterization of color lamellae in natural pink diamonds. Diamond & Related Materials, vol. 19, pp. 1207-1220.
Gaillou E., Wang W, Post J.E., King J.M., Butler J.E., Collins A.T., Moses T.M. (2010)The Wittelsbach-Graff and Hope diamonds: not cut from the same rough. Gems & Gemology, vol. 46, No 2, pp 80-88.
Rondeau B., Fritsch E., Mazzero F., Gauthier J.-P., Cenki-Tok B., Bekele E., Gaillou E. (2010) Play-of-color opal from Wegel Tena, Wollo Province, Ethiopia. Gems & Gemology, vol. 46, No 2, pp 90-105.
Gaillou E., Fritsch E., Aguilar-Reyes B., Rondeau B., Barreau A., Ostroumov M. (2008) Common gem opal: An investigation of micro- to nano-structure. American Mineralogist, vol. 93, pp. 1865-1873.
Gaillou E., Fritsch E., Notari F. (2008) Photoinduced absorptions of the H1b and H1c centers in some natural treated diamonds. Diamond and Related Materials, vol. 17, pp. 2029-2036.
Gaillou E., Delaunay A., Rondeau B., Bouhnik-Le Coz M., Fritsch E., Cornen G., Monnier C. (2008) The geochemistry of opals as evidence of their origin.
Gaillou E., Post J.E. (2008) An examination of the Napoléon diamond necklace. Gems and Gemology, vol. 43, n° 4, pp. 352-357. http://lgdl.gia.edu/pdfs/gemsandgemology/articles/Wi07-G&G-article-on-napoleon-diamond-necklace.pdf
Karampelas S., Gaillou E., Fritsch E., Douman M. (2007) Color-zoned andradite-demantoid from Iran, with calcite inclusions. Gems and Gemology, vol. 43, n° 1, pp. 65-67 .
Fritsch E., Gaillou E., Rondeau B., Barreau A., Albertini D., Ostroumov M. (2006) The nanostructure of fire opal. Journal of Non Crystalline Solids, vol. 352, pp. 3957-3960.
Gaillou E., Delaunay A., Fritsch E., Bouhnik-le-Coz M. (2006) Geologic origin of opals deduced from geochemistry. Gems & Gemology, vol. 42, n°3, p. 107.
Gaillou E., Rondeau B., Fritsch E., Bouhnik-Le-Coz M., Cornen G., Ostroumov M. (2005) Toward a geochemistry of opals. Geochimica et Cosmochimica Acta, vol. 69, n° 10, p. A279.
Gaillou E., Mocquet B., Fritsch E. (2004) A new material from
Fritsch E., Gaillou E., Ostroumov M., Rondeau B., Devouard B., Barreau A. (2004) Relationship between nanostructure and optical absorption in fibrous pink opals from Mexico and Peru. European Journal of Mineralogy, vol. 16, pp. 743-752.
III-2. OTHER PUBLICATIONS
Gaillou E.,Devouard B., Vielzeuf D., Boivin P., Rochault J., Valley J., Harris C. (2010)Les saphirs du Mont Coupet, de Menet et du Sioulot : trois gisements du Massif Central à caractéristiques pétrogénétiques contrastées. Le Règne Minéral, vol. 93, pp. 28-36.
Gaillou E, Post J.E. (2008)Smithsonian collection provides treasure store of gemstones. InColor, Spring 2008, pp. 31-34.
Karampelas S., Gaillou E., Fritsch E., Douman M. (2007) Les grenats andradites-démantoïdes d’Iran : zonage de couleur et inclusions. Revue de gemmologie a.f.g., vol. 160, pp. 14-20.
Gaillou E. (2006) L’opale : un nanomatériau naturel. Mensuel de l’Université, n°11, section « Études » (online only at http://www.lemensuel.net/L-opale-un-nanomateriau-naturel.html).
Gaillou E. (2006) Relations entre nanostructure, propriétés physiques et mode de formation des opales A et CT. Université de Nantes, France, PhD Thesis, 307pp. http://www.gemnantes.fr/recherche/theses/files/gaillou.php
Gaillou E. (2005) Nouvelles absorptions photoinduites dans les diamants : H1b, H1c et système à 4850 cm-1. Thesis of Gemological Diploma (diplôme d’Université de gemmologie), Université de Nantes, France, 50pp. . http://www.gemnantes.fr/documents/pdf/DUGs/Gaillou_DUG.pdf
Gaillou E. (2005) Nouvelles absorptions photoinduites dans le diamant : H1b, H1c et système à 4850 cm-1. Revue de gemmologie a.f.g., n° 155, p. 23.
Gaillou E. (2003) Étude minéralogique des saphirs du Sioulot, du Mont Coupet et de Menoyre ; détermination de leur origine géologique. Diplôme d’études approfondies, Université Blaise Pascal, France, 66pp. http://www.gemnantes.fr/documents/pdf/theses/DEA-Gaillou.pdf
Gaillou E., Shirey S.B., Bulanova G.P., Marks B., Smith C.B., Wang J., Kohn S.C., Walter M.J.. (2012) Sulfide inclusion re-os ages and carbon, nitrogen of diamonds from the Murowa kimberlites: implications for Zimbabwe craton evolution. 10th International Kimberlite Conference Extended Abstract No. 10IKC-212.
Bulanova G.P., Marks A., Smith C.B., Kohn S.C., Walter M.J., Gaillou E., Shirey S.B., Trautman R., Griffin B.J. (2012) Diamonds from Sese and Murowa kimberlites (Zimbabwe) – evidence of extreme peridotitic lithosphere depletion and Ti-REE metasomatism.
Gaillou E., Post J.E., Rose T., Butler J.E. (2011)Cathodoluminescence applied to natural, plastically deformed diamonds: low temperature and high spatial resolution matter. Cathodoluminescence 2011, Microanalysis Topic Conference, October 25-25 2011, Gaithersburg, MD (lecture). Abstract published by Microscopy and Microanalysis.
Gaillou E., Post J.E., Butler J.E. (2011)On the peculiarities of Australian and Venezuelan pink diamonds: influence of the geologic settings. Goldschmidt Conference, Prague, Czech Republick, August 14th-19th 2011. Abstract in Mineralogical Magazine, 75, 3,p. 882 (lecture).
Gaillou E., Post J.E., Rost D., Butler J.E. (2011)Boron concentration in natural type IIb blue diamond. Diamond Conference, Warwick, UK, July 4th-7th 2011. Extended abstract in book of abstract, not published: The 62nd Diamond Conference, Warwick 2011, pp O23.1-O23.3 (lecture).
Gaillou E., Post J.E., Steele A., Butler J.E. (2011) On the peculiarities of Australian and Venezuelan pink diamonds: influence of the geologic settings? Diamond Conference, Warwick, UK, July 4th-7th 2011. Extended abstract in book of abstract, not published: The 62nd Diamond Conference, Warwick 2011, pp O18.1-O18.3 (lecture).
Rondeau B., Fritsch E., Gauthier J.-P., Mazzero F., Bodeur Y., Cenki-Tok B., Gaillou E., Bekele E. (2010)Sur les conditions de genèse des opales du Wollo (Ethiopie). 23ème Réunion des Sciences de la Terre (RST 2010), Bordeaux, France, October 25th-29th 2010. Session 4-1: Gemology (lecture).
Devouard B., Paquette J.-L., Ricci J., Médard E., Boivin P., Gaillou E., Vielzeuf D., Rochault J. (2010) Saphirs et zircons gemmes d’Auvergne (Massif Central français) : occurrences, pétrogenèse, et géochronologie. 23ème Réunion des Sciences de la Terre (RST 2010), Bordeaux, France, October 25th-29th 2010. Session 4-1: Gemology (lecture).
Gaillou E., Rost D., Post J.E., Butler J.E. (2010)Quantifying Boron in Natural Type IIb Blue Diamonds. Goldschmidt Conference, Tennessee, Knoxville, June 13th-18th 2010. Abstract in Geochimica et Cosmochimica Acta, 74, 12, p. A313 (lecture).
Fritsch E., Gaillou E., Massuyeau F. & Rondeau B. (2010) Luminescence of Opals: A Witness to their Geochemistry. Goldschmidt Conference, Tennessee, Knoxville, June 13th-18th Juin 2010. Abstract in Geochimica et Cosmochimica Acta, 74, 12, p. A307 (lecture).
Fritsch E., Gaillou E., Massuyeau F. (2009) Luminescence of opals: a review of intrinsic and extrinsic emission. International Gemmological Conference, Arusha, Tanzanie. Abstract in Proceedings book. pp 17-18. 10-14 October (lecture).
Gaillou E., Post J.E., Bassim N., Rose T., Fries M., Stroud R., Butler J.E. (2009) Nature of the pink graining in natural diamonds. Diamond Conference,
Post J.E., Gaillou E., Eaton-Magana S.,
Gaillou E., Post J. E., Vicenzi E. P., Rose T., Bassim N., Stroud R. M., Butler J. E. (2008)Optical characterization of natural pink diamonds: a study of the type Ia non-Argyle pinks. Diamond Conference,
Gaillou E. (2008) Color in gem opals. Conference at the Mineralogical Society of
Gaillou E. (2008) Color in gem opals. 1417th Meeting of the Geological Society of
Gaillou E. (2008) An examination of the Napoléon necklace. Mineral Sciences lecture, Smithsonian Institution, June 6th, 2008.
Gaillou E., Fritsch E., Notari F. (2007)Photoinduced absorptions of the H1b and H1c centers in some natural treated diamonds. Diamond Conference,
Fritsch E., Gaillou E., Rondeau B., Ostroumov M., Aguilar-Reyes B., Barreau A., Albertini D. (2007) Shining new lights on opals. Annual Conference of the Scottish Branch of Gemmological Association,
Fritsch E., Rondeau B., Gaillou E., Gauthier J.-P., Massi L. (2007)Questions actuelles sur l’apparence colorée des matériaux gemmes. GDR Couleur, March 14th, CNRS, Paris, France (lecture).
Gaillou E. (2006) Inclusions minérales dans les saphirs : aide à la détermination de l’origine géologique et géographique. Scientific days on vitreous inclusions,
Gaillou E., Delaunay A. Fritsch E., Bounik-Le Coz M. (2006) Geologic origin of opals deduced from geochemistry. Gemological Research Conference (GRC), August 26th-27th,
Gaillou E., Fritsch E., Notari F. (2005) New photoinduced absorptions in diamonds: H1b, H1c and 4850 cm-1 system. Diamond 2005, 16th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes and Nitrides, Toulouse, France, Septembre 11th-16th 2005. Abstract in the book of abstracts, unpublished, ref [15.4.10] (poster), p. 15.4.10.
Gaillou E., Rondeau B., Fritsch E., Bouhnik-Le-Coz M., Cornen G., Ostroumov M. (2005) Toward a geochemistry of opals. Goldschmidt Conference 2005, 20-25 May,
Gaillou E., Fritsch E., Rondeau B., Aguilar B.O., Faulques E., Ostroumov M. (2005) L’opale, un nanomatériau naturel. Colloque Matériaux Pays de la Loire. La Chapelle/Erdre, Juillet 8th-9th (poster).
Gaillou E. (2005) Les saphirs magmatiques du Massif Central. VIes Rendez-Vous Gemmologiques de Paris, March 5th, Paris, France (lecture). Invited speaker.
Fritsch E., Ostroumov M., Rondeau B., Aguilar-Reyes B.O., Barreau A., Gaillou E., Albertini D., Wery J. (2003) Nano- to micro-structure of natural gem opals: relation to deposition and growth conditions. Materials Research Society Fall 2003. Boston, MA, USA (lecture).