Glossary of gemological terms

Gemstones have been captivating humanity for centuries with their exquisite beauty and intrinsic value. However, delving into the world of gemology can be overwhelming due to the specialized terminology associated with it. In this article, we will provide you with a comprehensive glossary of gemological terms to help you navigate this fascinating realm.

What is Gemology?

Gemology, often referred to as gemological science, is the scientific study and examination of gemstones. It encompasses a wide range of disciplines, including mineralogy, geology, chemistry, and artistry. Gemologists analyze the physical, optical, and chemical properties of gemstones to identify and evaluate their quality and value.

Importance of gemological terms

Understanding gemological terms is crucial for anyone involved in the world of gemstones, from gem collectors and jewelry enthusiasts to gemstone dealers and appraisers. These terms provide a common language for describing and discussing gemstones accurately.

A - Z: Glossary of gemological terms

A. Abrasion

Abrasion refers to the wearing away of a gemstone's surface due to friction and contact with other materials. This can affect a gem's polish and overall appearance.

B. Birefringence

Birefringence is a gemological term describing a gemstone's ability to split light into two distinct rays as it passes through. This phenomenon is often observed in gemstones like calcite and zircon.

C. Carat

Carat is a unit of measurement used to quantify a gemstone's weight. One carat is equivalent to 200 milligrams. It is an essential factor in determining a gemstone's value.

D. Dispersion

Dispersion refers to the ability of a gemstone to separate light into its spectral colors, creating a beautiful play of colors. This is commonly seen in gems like diamonds and sapphires.

E. Enhancements

Enhancements encompass any treatments or modifications made to a gemstone to improve its appearance or durability. Common enhancements include heat treatment and filling of surface-reaching fractures.

F. Facet

Facet is a flat, polished surface on a gemstone that enhances its brilliance and appearance. Gem cutters carefully shape and arrange facets to maximize a gem's beauty.

G. Grading

Grading involves evaluating a gemstone based on factors such as color, clarity, cut, and carat weight. It helps determine a gem's quality and value.

H. Hardness

Hardness is a measure of a gemstone's resistance to scratching. The Mohs scale, ranging from 1 (softest) to 10 (hardest), is commonly used to assess gemstone hardness.

I. Inclusion

Inclusion refers to internal imperfections or foreign materials within a gemstone. These inclusions can affect a gem's transparency and overall value.

J. Jewelry

Jewelry encompasses any decorative items, such as rings, necklaces, and earrings, created using gemstones. It is a means of showcasing the beauty of these precious gems.

K. Kimberlite

Kimberlite is a type of volcanic rock that often contains diamonds. Gemologists study kimberlite deposits to locate diamond sources.

L. Luster

Luster describes the appearance of a gemstone's surface when it reflects light. It can be categorized as metallic, adamantine, vitreous, or silky, depending on the gem's properties.

M. Mohs Scale

The Mohs Scale is a relative scale used to measure the hardness of minerals and gemstones. It ranges from 1 (talc) to 10 (diamond), with each level representing a higher degree of hardness.

N. Noble Metals

Noble metals are metals that are resistant to corrosion and oxidation. They are often used in the settings of precious gemstone jewelry to maintain their beauty.

O. Organic Gem

An organic gem is a gemstone formed from organic materials, such as pearls, amber, and coral. These gems have unique properties and origins.

Why understanding these terms matters

Gaining familiarity with these gemological terms empowers individuals to make informed decisions when buying, selling, or appraising gemstones. Whether you're a gem collector looking for rare specimens or a jeweler creating custom pieces, a solid grasp of these terms is invaluable.

Gemology in practice

In practice, gemologists utilize their knowledge of these terms to assess the quality, value, and authenticity of gemstones. They employ various tools and techniques, including gemological microscopes, spectrometers, and refractometers, to conduct thorough examinations.

A valuable resource for  gemologists

In conclusion, the world of gemology is a rich and fascinating one, filled with a multitude of specialized terms and concepts. This glossary serves as a valuable resource for anyone seeking to navigate this realm with confidence. Whether you're an aspiring gemologist or simply an enthusiast, understanding these terms will enhance your appreciation of the world's most exquisite gemstones.


  1. What is the most valuable gemstone in the world? The value of a gemstone depends on various factors, but some of the most valuable gemstones include diamonds, rubies, and emeralds.

  2. Are all gemstones naturally occurring? No, some gemstones can be created synthetically in laboratories, but natural gemstones are often considered more valuable.

  3. How can I tell if a gemstone is genuine? Gemologists at IIGL (Institute of International Gemological Laboratory) use a combination of tests, including visual inspection and specialized equipment, to determine the authenticity of gemstones.

  4. What is the rarest gemstone in the world? Some of the rarest gemstones include red diamonds, jadeite jade, and blue garnets.

  5. Can gemstones be damaged easily? Gemstones vary in hardness, so some are more prone to damage than others. It's important to handle them with care and avoid exposing them to harsh chemicals or extreme heat.

Visit the recently inaugurated gemological laboratories of IIGL

  1. IIGL Kolkata
  2. IIGL Varanasi
  3. IIGL Tata Nagar
  4. IIGL Bhubaneshwar
  5. IIGL Brahampur