Abstract
Raman and photoluminescence (PL) mapping is a non-destructive method which allows gemologists and scientists to evaluate the spatial distributions of defects within a gem; it can also provide a method to quickly distinguish different species within a composite gem. This article provides a summary of this relatively new technology and its instrumentation. Additionally, we provide a compilation of new data for various applications on several gemstones. Spatial differences within diamonds can be explored using PL mapping, such as radiation stains observed on the rough surface of natural green diamonds. Raman mapping has proven useful in distinguishing between omphacite and jadeite within a composite of these two minerals, identifying various tourmaline species within a heterogeneous mixture, and determining the calcium carbonate polymorphs in pearls. Additionally, it has potential to be useful for country-of-origin determination in blue sapphires and micro-inclusion analysis. As new avenues of research are explored, more applications for gem materials will inevitably be discovered.
Highlights
Gemological laboratories rely on non-destructive analytical techniques that are generally based on optical methods such as absorption spectroscopy along with Raman and photoluminescence (PL) spectroscopy
PL and Raman spectroscopy, as used for gemstones, is a microscope-assisted analytical technique in which a material is illuminated with laser light and the resulting emission is measured with a high-resolution spectrometer
Whether gemologists are searching for rare corundum inclusions in gem quality diamonds or finding inclusions that originated from the sub-lithosphere, using a Raman imaging microscope can be a greatare tool diamond inclusion our knowledge, these inclusions thefor second occurrence of identification
Summary
Gemological laboratories rely on non-destructive analytical techniques that are generally based on optical methods such as absorption spectroscopy along with Raman and photoluminescence (PL) spectroscopy. Raman and PL mapping is a logical extension of these methods in which spectra can be collected quickly and automatically across an area instead of a single point (or the sample manually moved to collect multiple spectra across a sample) These mapping techniques have become possible in the past few years as the technology for the necessary instrumentation has improved. Raman and PL mapping have become ideal methods to analyze the spatial differences in these diamonds and similar diamonds that are distinguished by distinct growth regions This new instrumentation automatically collects hundreds to thousands of spectra across a sample and has provided several new, exciting research opportunities and identification avenues in recent years. It offers an indication of the variety of research possibilities across the breadth of the gemological world
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