Spectroscopic and crystallographic analysis of nephrite jade gemstone using laser induced breakdown spectroscopy, Raman spectroscopy, and X-ray diffraction

Our plain-English summary of Spectroscopic and crystallographic analysis of nephrite jade gemstone using laser induced breakdown spectroscopy, Raman spectroscopy, and X-ray diffraction, by R.A. Khan, M. Anwar-Ul-Haq, M. Qasim, et al (Heliyon, 2022).

The study

• Authors: R.A. Khan, M. Anwar-Ul-Haq, M. Qasim, M.S. Afgan, S.U. Haq, S.Z. Hussain
• Journal: Heliyon
• Published: 2022;8(11):e11493
• Read it: PubMed · Publisher · Free full text

Abstract

The elemental composition, mineral phases, and crystalline structure of nephrite jade were investigated using calibration-free laser-induced breakdown spectroscopy (CF-LIBS), Raman spectroscopy, and X-ray diffraction (XRD). For compositional analysis, the laser-induced plasma was generated on the surface of nephrite jade. The plasma emissions were then acquired and analyzed, which revealed several elements in the sample, including Si, Mg, Ca, Li, Fe, Al, Na, K, and Ni. The plasma temperature was extracted from the Boltzmann plot before and after two-step self-absorption correction, and used in CF-LIBS calculations to get the elemental concentration. After self-absorption correction, the quantitative results obtained using CF-LIBS were found to be in close agreement with ICP-OES. The Raman spectrum of nephrite jade exhibits Si-O and M-OH stretching vibrations in the regions of 100 cm-1 to 1200 cm-1 and 3600 cm-1 to 3700 cm-1, respectively, whereas the XRD spectrum revealed the monoclinic crystalline phase of tremolite.

© 2022 The Author(s).

In plain English

This laboratory study analyzed one sample of nephrite jade, a gemstone, from nephrite ore mines in the Bajaur district of KPK province, Pakistan. The authors measured which chemical elements it contained using a laser-based method (calibration-free laser-induced breakdown spectroscopy, CF-LIBS). They corrected those measurements in two steps for a distortion called self-absorption, then compared them with a second chemical method (ICP-OES). They also used Raman spectroscopy and X-ray diffraction to identify the mineral. A scanning electron microscope image showed fine, randomly aligned tremolite bundles. The laser method detected silicon, iron, calcium, magnesium, sodium, lithium, aluminum, nickel and potassium. After the second correction it gave relative concentrations, as weight percentages shared among those nine elements, of silicon 57.96%, calcium 19.12%, magnesium 14.17% and iron 5.59%, compared with 57.89%, 18.70%, 14.27% and 6.12% by ICP-OES. The Raman and X-ray results showed the sample was mainly tremolite amphibole, which has a monoclinic crystal structure. The authors concluded that the corrected laser results agreed well with ICP-OES. They noted that trace elements were measured less accurately. The article did not discuss asbestos, airborne fibers, or health.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory analytical study of a mineral sample (elemental analysis by CF-LIBS checked against ICP-OES, plus Raman spectroscopy, X-ray diffraction and electron microscopy); no human subjects
• Who was studied: One sample of nephrite jade from nephrite ore mines in the Bajaur district, KPK province, Pakistan; light to dark green with small white spots
• Exposure: No human exposure was studied. The material analyzed was nephrite jade, which the authors found to be mainly tremolite amphibole; electron microscopy showed fine, randomly aligned tremolite bundles of different sizes and shapes
• Main results:
  • The laser spectrum of the sample showed emission lines of Si, Fe, Ca, Mg, Na, Li, Al, Ni and K
  • The concentrations reported are relative concentrations (weight percent) of the nine measured elements, each method's values adding to about 100%
  • After the second self-absorption correction, CF-LIBS gave relative concentrations of silicon 57.96%, magnesium 14.17%, calcium 19.12% and iron 5.59% in the nephrite jade sample
  • ICP-OES gave relative concentrations of Ca 18.70, Fe 6.12, Mg 14.27 and Si 57.89 wt.% for the same sample
  • Average plasma temperature was 24000 K before correction, 17750 K after the first correction and 15800 K after the second correction
  • Raman spectroscopy showed that tremolite was the main mineral phase in the sample
  • X-ray diffraction peaks matched the tremolite reference card. The authors concluded the sample was mainly tremolite amphibole, which has a monoclinic structure (a = 9.8 Å, b = 18.0 Å, c = 5.2 Å, beta = 104.7 degrees)
• The authors' conclusion: The authors concluded that CF-LIBS results after the second self-absorption correction agreed well with ICP-OES, and that XRD confirmed tremolite crystals in the nephrite jade. They wrote that LIBS has potential as an alternative technique for analysis in mines and ores.
• Limitations the authors state:
  • Trace elements were measured less accurately than the principal elements and showed relatively higher errors
  • The plasma temperature had an uncertainty of about 10%
  • Matching standard reference materials were not available, so the calibration-free method was used instead of the calibration-based approach

Topics

Medical terms in this study, explained in our Lexicon: Crystallographic Analysis, X-Ray Diffraction (XRD), Crystalline, Monoclinic, Tremolite.

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