Rough Gemstone Identification - World Gemological Institute
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Rough Gemstone Identification


When it comes to rough stone identification, WGI employs a comprehensive approach that combines scientific analysis, advanced gemological tools, and extensive gemstone knowledge. Here’s an overview of how WGI conducts rough stone identification:


  1. Visual Examination: WGI gemologists begin by visually inspecting the rough stone. They assess its color, transparency, shape, and surface features. They look for any distinctive characteristics or inclusions that can provide clues about its identity, origin, or treatment.
  2. Physical Properties: WGI gemologists analyze various physical properties of the rough stone, including hardness, cleavage, fracture, and specific gravity. We use specialized tools and equipment to determine the stone’s hardness on the Mohs scale, evaluate its cleavage and fracture patterns, and measure its specific gravity. These properties help narrow down the possibilities and differentiate between different gemstone types.
  3. Refractive Index and Optics: WGI gemologists utilize refractometers to measure the refractive index of the rough stone. This information helps determine the gemstone’s identity by comparing the obtained refractive index value with known gemstone data. Additionally, gemologists assess the stone’s optical phenomena, such as birefringence, pleochroism, or dispersion, which can provide further insights into its identification.
  4. Spectroscopic Analysis: WGI employs advanced spectroscopic techniques to analyze the rough stone’s spectral characteristics. Gemologists use tools like spectrometers to examine the stone’s absorption and emission spectra. This analysis helps identify specific elements or impurities present in the gemstone, which can be crucial in distinguishing between similar-looking stones or identifying treatments.
  5. Microscopic Examination: WGI gemologists conduct thorough microscopic examinations of rough stones. We use high-powered microscopes to study internal features, such as inclusions, growth patterns, and crystal structure. These observations aid in identifying the gemstone species, evaluating its quality, and determining if it has undergone any treatments or enhancements.
  6. Advanced Gemological Testing: In cases where further testing is required, WGI gemologists may employ additional specialized techniques. For example, they might use advanced tools like X-ray diffraction (XRD) to analyze the crystal structure of the rough stone, infrared spectroscopy (FT-IR) to identify certain functional groups or mineral components, or energy-dispersive X-ray fluorescence (EDXRF) to determine the elemental composition.
  7. Gemstone Database and Expertise: WGI gemologists have access to extensive gemstone databases and reference materials. We rely on our knowledge and experience, cross-referencing the data obtained from their examinations with established gemological information. This helps ensure accurate identification and classification of the rough stone.
  8. Certification and Reporting: Upon completing the rough stone identification process, WGI provides a detailed gemological report. The report includes information about the stone’s identification, characteristics, treatments (if any), and other relevant data. This certification serves as a valuable document for buyers, sellers, and collectors, providing assurance and transparency regarding the rough stone’s identity and quality.


The World Gemological Institute’s rigorous approach to rough stone identification combines scientific methods, cutting-edge technology, and the expertise of its gemologists. Through our meticulous analysis, WGI aims to provide reliable and trustworthy identification reports, contributing to the integrity and transparency of the gemstone industry.