Application of portable Raman instruments for fast and non-destructive detection of minerals on outcrops

Our plain-English summary of Application of portable Raman instruments for fast and non-destructive detection of minerals on outcrops, by J. Jehlicka, P. Vítek, H.G. Edwards, et al (Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy, 2009).

The study

• Authors: J. Jehlicka, P. Vítek, H.G. Edwards, M. Heagraves, T. Capoun
• Journal: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
• Published: 2009;73(3):410-9
• Cited by: 32 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Raman spectral signatures have been obtained in situ for a series of minerals using portable Raman instruments. Cerussite, anglesite, wulfenite, titanite, calcite, tremolite, andradite and quartz were detected using portable Raman spectrometer First Defender XL (Ahura). Baryte, almandine and realgar Raman spectra obtained by this instrument in the field were compared to the data measured by the other mobile Raman instrument Inspector Raman (DeltaNu). Bench Raman dispersive microspectrometer (InVia Reflex, Renishaw) was used for comparative purposes. All spectra were obtained using a 785nm diode excitation. Although displaying lower spectral resolution comparing with the laboratory confocal instrument both portable instruments permit unambiguous detection of minerals in the field. These possibilities designate portable Raman machines as excellent tools for field geological applications. Miniaturised Raman instrument combined with LIBS will be included in the payload of the EXO Mars mission and would open interesting research possibilities in other in situ field planetary studies.

In plain English

This methods study tested whether small portable Raman spectrometers can identify minerals directly on rock outcrops. These instruments identify a mineral from the way it scatters laser light. The authors examined eleven minerals, including the amphibole mineral tremolite. The specimens came from the Mineralogical Collection of Charles University in Prague and from localities at Vlastějovice and Bohdaneč in the Czech Republic. Two portable instruments, the First Defender XL (Ahura) and the Inspector Raman (DeltaNu), were compared with a laboratory bench instrument (Renishaw InVia Reflex), all using 785 nm laser light. For tremolite, the portable instrument's spectra agreed with the bench instrument's, but the signal was noisier. The portable instruments had lower resolution and a narrower range, so some bands were merged or missed. During sunny spring weather in the first field campaign, spectra could not be obtained unless the instrument head was covered. Two lead minerals, cerussite and pyromorphite, produced false features above 1100 wavenumbers with 785 nm light. The authors concluded that nine minerals were detected unequivocally and that portable instruments can be recommended for field detection. The article does not discuss asbestos 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: Instrument methods study comparing portable and laboratory Raman spectrometers on mineral specimens, in the laboratory and in the field
• Who was studied: Eleven minerals (calcite, quartz, andradite, tremolite, anglesite, wulfenite, almandine, baryte, realgar, cerussite, pyromorphite). Specimens came from the Mineralogical Collection of Charles University in Prague and from Vlastějovice and Bohdaneč, Czech Republic. Calcite, quartz, andradite and tremolite were measured directly on outcrops at the Vlastějovice and Bohdaneč quarries. No people were studied.
• Exposure: No human or animal exposure was studied. The study compared measuring instruments: the portable First Defender XL (Ahura) and Inspector Raman (DeltaNu) against the bench Renishaw InVia Reflex, all using 785 nm diode laser excitation. Tremolite is one of the minerals measured.
• Main results:
  • For tremolite, the portable First Defender XL gave spectra consistent with the bench instrument, with a lower signal to noise ratio. It showed a strong band at 676 per centimetre and medium bands at 225 and 1061 per centimetre.
  • The authors measured spectral resolution with a neon lamp. Band widths were 7 to 10 per centimetre for the Ahura instrument and 6 to 9 for the DeltaNu instrument, compared with 3 to 8 for the bench instrument.
  • For realgar, several bands appeared only as shoulders of a strong band on the portable instrument but were clearly separated on the bench instrument. The authors took this as showing lower resolution in the First Defender XL.
  • For almandine, the First Defender XL gave a notably lower quality signal than the laboratory instrument, and its automatic mode could not be used. The Inspector Raman gave a better signal to noise ratio for almandine.
  • The two portable instruments showed no significant differences in the baryte signal over repeated measurements.
  • During sunny spring weather in the first field campaign, successful spectra could not be obtained without covering the instrument head. All measurements were done using black tissue for shade. The best distance between the specimen and the instrument window was 2 to 10 mm.
  • With 785 nm excitation, cerussite and pyromorphite produced broad false (non-Raman) features on all instruments. The authors stated that identification was still possible using only bands below 1100 per centimetre.
• The authors' conclusion: The authors concluded that calcite, quartz, andradite, tremolite, anglesite, wulfenite, almandine, baryte and realgar were detected unequivocally. They concluded that portable Raman instruments can be recommended as a fast and easy way to detect minerals in the field.
• Limitations the authors state:
  • Because the portable instruments had a limited spectral range, some of the lowest bands could not be recorded. For example, the 157 per centimetre calcite band seen by the laboratory instrument was outside the First Defender XL's range.
  • Field measurement raised practical issues, including sunlight on the sample and the positioning of the instrument head.
  • The 785 nm excitation produced non-Raman artifacts for cerussite and pyromorphite.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Tremolite.

Medical terms in this study, explained in our Lexicon: Tremolite.

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