Introduction to Gemology: Practical Aspects

Study Notes

Gemology is the science of identifying, evaluating, and appraising gemstones.
It involves studying the physical and chemical properties of gems, including their optical, mechanical, and thermal characteristics.
Practical experience is crucial for understanding and applying gemological knowledge in real-world scenarios.

Identifying gemstones involves using various methods and tools.
Visual examination: observing the gemstone's appearance; color, clarity, shape (i.e., crystallographic forms) etc.
Instrumental analysis: employing instruments like spectrometers, refractometers, polariscopes and UV lamps to measure and analyze physical properties..
Refractive Index: The measure of how light bends as it passes through a gemstone. This varies with the gem type. Refractometers are used to determine refractive index.
Specific Gravity: The ratio of a gem's weight to the weight of an equal volume of water. This value helps to differentiate gems. Specific gravity is often measured using a calibrated scale or special tools.
Color: Gemstones exhibit a wide range of colors, often due to trace elements. Careful observation and comparison of colors under different light sources is essential.
Clarity: The degree of imperfections (inclusions and blemishes) in a gemstone. Differences in clarity greatly affect value. Identifying and analyzing inclusions/blemishes involves high magnification and careful observation.
Cut and Polish: The shape and facets of a gemstone, significantly affecting its brilliance, fire, and scintillation. Different cuts produce various optical effects. Analysis of the cut, its influence on the gem's appearance, and the precision of polish.

Hardness: Resistance to scratching, with Mohs Hardness Scale used to compare relative hardness.
Fluorescence: Emission of light when exposed to ultraviolet (UV) radiation. UV lamps are used to detect this and determine color characteristics under UV light, in combination with other properties like fluorescence emission wavelength, associated color, etc
Specific gravity is determined by dividing the weight of the gem by the weight of an equal volume of water . Common methods are using calibrated scales or special tools.

Recognizing treated and enhanced gemstones is essential.
Heat treatments, irradiation, dyeing, filling cracks/inclusions, and other processes alter the original characteristics of gems.
Observational tests should be combined with sophisticated laboratory techniques and reference data to identify and assess the extent, type and origin of treatments.

Identifying various gemstones using a refractometer, spectroscope, UV lamp, and loupes to ascertain characteristics including color, clarity and inclusion/blemishes
Comparing and contrasting different gem samples visually and with instruments, measuring physical properties like hardness, refractive index, and specific gravity.
Identifying synthetic versus natural gemstones through a combination of visual and instrumental analyses
Evaluating gem cuts and polish to assess the quality of facets and their effect on brilliance.
Determining the effect of treatments on gem characteristics (color, clarity, and refractive index).

Ethical sourcing and responsible gem trading practices are crucial.
Knowing the origin of a gemstone helps ensure ethical and sustainable practices in the supply chain.
Understanding potential environmental impacts from mining and gemstone production locations.

Techniques like Fluorescence, UV and light absorption spectroscopy, Raman spectroscopy, and microscopy may be used in the identification and characterization of gemstones.
These advanced techniques need to be used in conjunction with all other techniques available for the thorough assessment of a particular gem.

Understanding the ethics of gem trading, especially issues related to conflict minerals and fair trade.
The importance of accurate gemstone grading and identification in promoting ethical and responsible practices in the gem trade