On the beauty of defects

In its pure and perfect form, diamond is colorless. However, in nature or even when made in a laboratory, diamonds are never composed just of perfectly arranged carbon atoms. At the atomic level even colorless and seemingly flawless diamonds contain trace amounts of other elements such as nitrogen or hydrogen, or they may contain structural defects such as missing carbon atoms. When present in specific atomic arrangements and concentrations, most minor components of defects can cause absorption of specific wavelengths that give rise to color

Color in Natural Diamonds: The Beauty of Defects

In its pure form, diamond is colorless. However, in nature (or even when made in laboratories), diamonds are never composed of 100 percent carbon atoms. Even colorless diamonds will contain some defects: missing carbon atoms or containing trace amounts of nitrogen or hydrogen, for example. When present in certain atomic arrangements and concentrations, most minor components cause absorption of specific wavelengths of light, giving rise to color. The color in diamond is not source specific, even if some mines are known to produce more of certain colors, such as blue diamonds from the Premiere mine in South Africa, or brown and pink diamonds from the Argyle mine in Australia. Virtually every single diamond mine could produce any kind of colored diamond. At auction, record prices for gems are currently held by pink and blue diamonds: for example, $2,155,332 per carat for a 24.78-carat Fancy vivid pink diamond (sold at Sotheby's in 2010) and$1.8 million per carat for a 5.3-carat Fancy deep blue diamond (sold at Bonhams in London in April 2013)

Combination of ERDA, FTIR spectroscopy and NanoSIMS for the characterization of hydrogen incorporation in natural diamonds

International audienceHydrogen is a volatile element involved in several geological processes ranging from rock weakening to the initiation of tectonic plates. Because it is present in diamond, the investigation of hydrogen content in natural diamonds could provide valuable information. Such studies are scarce despite hydrogen being among the main impurities in their structure. Using Elastic Recoil Detection Analysis, Fourier Transform Infrared spectroscopy and Nanoscale Secondary Ions Mass Spectrometry, we analyzed the incorporation of hydrogen in three diamonds growth habits: octahedral, cuboid and fibrous. Up to 25 wt. ppm of hydrogen was measured in some samples, placing hydrogen as the second most abundant impurity in natural diamonds after nitrogen and before boron. Comparison between the three methods indicates a difference in the main mode of hydrogen incorporation depending on the growth habit. Hydrogen is more readily incorporated in the fibrous and cuboid habits compared to the octahedral one. We also show that the incorporation of hydrogen is not correlated with the incorporation of nitrogen. Results suggest no chemical equilibration of hydrogen by diffusion through geological times and also confirm that not all hydrogen may be infrared active

A Gemological and Spectroscopic Study with Mobile Instruments of “Emeralds” from the Coronation Crown of Napoleon III

International audienceForty-five “emeralds,” formerly set in the coronation crown of Napoleon III, were studied using nondestructive mobile spectroscopic and gemological means. Adorned with emeralds, diamonds, and gold, the crown was created in 1855 by royal jeweler Alexandre Gabriel Lemonnier but dismantled in 1887 for the auctioning of the French crown jewels. Some of the emeralds were donated to the École des Mines (Paris School of Mines, now known as Mines Paris - PSL) in 1887, prior to the auction. Our examination revealed that 41 out of 45 gems were indeed natural emeralds, presenting no evidence of clarity enhancement. Their gemological characteristics and age suggest a Colombian provenance. The other four samples were determined to be artificial glass containing iron and/or copper and possibly other chromophores. These glass imitations could have been set when the crown was created or shortly thereafter. This study is part of an effort to examine gemstones of historical meaning and significance worldwide

Non-Destructive Study of Egyptian Emeralds Preserved in the Collection of the Museum of the Ecole des Mines

In the present study, rough emerald single crystals and rough emeralds in the host rock from the ruins of Alexandria and from the Mount Zabargad in Egypt, preserved in the collection of the museum of the Ecole des Mines (Mines Paris—PSL) since the late 19th or early 20th century, are investigated. All samples were characterized by non-destructive spectroscopic and chemical methods during a week-long loan to the LFG. Raman, FTIR and UV-Vis-NIR spectroscopy revealed that Egyptian emeralds contain H2O molecules accompanied by relatively high concentrations of alkali ions and are colored by chromium and iron. Additionally, EDXRF showed that the emeralds from Egypt contain up to 84 ppm Rb and low amounts (below 200 ppm) of Cs. Inclusions and parts of the host rock were also observed under optical microscope and analyzed with Raman spectroscopy. Tube-like structures, quartz, calcite, dolomite, albite and phlogopite are associated minerals, and inclusions are identified in these historic emeralds from Egypt. This work will hopefully further contribute to the characterization of emeralds of archaeological significance

Non-Destructive Study of Egyptian Emeralds Preserved in the Collection of the Museum of the Ecole des Mines

In the present study, rough emerald single crystals and rough emeralds in the host rock from the ruins of Alexandria and from the Mount Zabargad in Egypt, preserved in the collection of the museum of the Ecole des Mines (Mines Paris—PSL) since the late 19th or early 20th century, are investigated. All samples were characterized by non-destructive spectroscopic and chemical methods during a week-long loan to the LFG. Raman, FTIR and UV-Vis-NIR spectroscopy revealed that Egyptian emeralds contain H2O molecules accompanied by relatively high concentrations of alkali ions and are colored by chromium and iron. Additionally, EDXRF showed that the emeralds from Egypt contain up to 84 ppm Rb and low amounts (below 200 ppm) of Cs. Inclusions and parts of the host rock were also observed under optical microscope and analyzed with Raman spectroscopy. Tube-like structures, quartz, calcite, dolomite, albite and phlogopite are associated minerals, and inclusions are identified in these historic emeralds from Egypt. This work will hopefully further contribute to the characterization of emeralds of archaeological significance