Raman analysis of minerals

Raman spectroscopy is widely used in the study of natural and synthetic materials in solid or liquid states or in the gas phase. It is a 3D in-situ nondestructive technique that provides data quickly, does not require special conditions for performing analyses, and can be carried out directly on the sample without any preparation. For these reasons, Raman spectroscopy is becoming increasingly popular in the analysis of mineralogical samples but is also used in many other fields including engineering, physics, pharmaceutical sciences, biology, and material sciences.

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As with infrared spectroscopy, Raman spectroscopy provides information about the structure of molecular vibrational energy levels. The set of these energy values, that is usually described in terms of frequency by the relation E=hʋ, is specific to each molecular species and constitutes a kind of "fingerprint " of the molecule, functional group, or mineral as a whole. The principle is simple: laser radiation interacts with a small area of the sample, the scattered light is collected by the microscope, appropriately filtered, and is then analyzed by the spectrometer. Raman and infrared spectroscopy make it possible to uniquely identify the chemical composition and structure of the material being analyzed. By combining an optical microscope with a Raman spectrometer, "Raman microscopy" can be used to image particular regions on or within samples and then analyze those regions (e.g. inclusions and intergrowths in minerals) with spatial resolution of less than 1 µm.

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About RCH V1.0

The RCH program is a user-friendly and versatile program that allows users to process their spectra using a variety of methods including,  baseline corrections, smoothing, normalization, frequency calibration, add/subtract/replace functions, derivative determination, fitting and spectrum ID via comparison with a independent, on-board Raman database (RCHDB).

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For more information about how you can use RCH v1.0 to process your Raman spectra consult the RCH User-Guide and/or RCH Paper, these can be accessed at the download page here:

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The RamanCrystalHunter Database (RCHDB)

In order to interpret the spectrum obtained from Raman analysis, that is, to be able to identify the mineral being analyzed, it is usually necessary to process the spectrum such that it can be compared with spectra stored in a database. For minerals, the largest Raman database is currently accessible at www.RRUFF.info from which one can also download the CrystalSleuth program that allows preliminary processing and automatic comparison with an internal database. This database however, is limited compared to the entire RRUFF list and is not regularly updated and thus spectral matches and subsequent mineral identification is not always exhaustive. Moreover, many spectra in the RRUFF database are low quality and/or poorly described and may produce unreliable matches. 

 

We are currently building a new comprehensive database of high-quality Raman spectra (The RCHDB) that is integrated within the RCH V1.0 software that allows users to accurately and efficiently identify their unknown minerals. The RCHDB will be regularly updated and improved.

 

We strongly encourage users of RCH to

 

[1] submit new spectra that are not currently included in the database.

 

[2] submit spectra that are of higher quality than those currently included in the database.

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