Raman and Photoluminescence Mapping of Gem Materials

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.

Disordered dolomite as an unusual biomineralization product found in the center of a natural Cassis pearl

“…Raman and photoluminescence mapping have been proved to be particularly useful in many gem identification applications, including pearls [ 32 ]. The Raman maps shown in Fig 5A displayed intensity variation at 705 cm −1 , which is a characteristic peak for aragonite.…”

Evading the Illusions: Identification of False Peaks in Micro‐Raman Spectroscopy and Guidelines for Scientific Best Practice

“…Raman spectroscopy has developed into a widely used and versatile tool in scientific research. It is used in a large variety of disciplines including chemistry, [1] physics, [2,3] biology, [4] geology, [5] gemology, [6] and medicine. [4] In material science, the pharmaceutical industry, and geology it has become a standard tool for research, especially in identification and distribution analysis of molecules, materials, and minerals.…”

Gemstone Inclusion Study by 3D Raman-Mapping and High-Resolution X-ray Computed Tomography: The Case of Trapiche Emerald from Swat, Pakistan

“…Additionally, less common minerals can also be detected by Raman, such as palygorskite fibers in pink opals from Mexico and Peru [10] and diopside needles in demantoids from Russia [11]. More inclusion identification cases and related references can be detailed in previous literature [12,13].…”