An Introduction to Gemology


The basic building blocks of understanding the science of gemstones.

Jade Color Trade Names

Jade Color Trade Names

Jade color trade names describe prized hues and patterns in jadeite and nephrite stones. Learn about the most popular and...
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Maw Sit Sit Guide

Maw Sit Sit Guide

Learn everything you need to know about maw sit sit, a rare, vibrant green gem rock used to make beautiful...
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How Does Jade Form?

How Does Jade Form?

The minerals known as jade, jadeite and nephrite, appear similar but have different properties. Learn how these materials form geologically....
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Does Chrysoprase Jewelry Fade?

Does Chrysoprase Jewelry Fade?

Should you wear chrysoprase jewelry only at night to protect the gem’s striking green color? Learn the facts here.
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Gemstone Care Guide

Gemstone Care Guide

Our gemstone care guide covers many popular gems. Learn how best to maintain your gemstone jewelry and what kinds of...
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An Introduction to Gem Identification

An Introduction to Gem Identification

Gem identification is part detective work, part art. Learn how gemologists can distinguish gem species and determine whether a stone...
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What are Lab-Grown Sapphires?

What are Lab-Grown Sapphires?

Learn how lab grown sapphires are made and how gemologists can distinguish natural from synthetic sapphires.
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Natural Pearls vs Cultured Pearls

Natural Pearls vs Cultured Pearls

Many consumers don’t understand the difference between natural pearls and cultured pearls. Learn what these terms mean and how to...
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A World of Crystals

A World of Crystals

We live in a world of crystals. Learn what they are and where you can find them, from deep underground...
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Top Spots for Gem Hunting in the US

Top Spots for Gem Hunting in the US

Visit one of the top gem hunting spots in the US. Go alone or with the family. A gemology-themed vacation...
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Gem Formation: How are Gemstones Created?

Gem Formation: How are Gemstones Created?

Gem formation usually involves mineral crystallization and other geological processes. Learn how these affect the gemstone properties gemologists study.
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An Introduction to Gemstone Inclusions

An Introduction to Gemstone Inclusions

Gemstone inclusions are materials trapped inside gems as they form. Learn how gemologists use inclusions to help identify gemstones and...
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What are Crystal Systems and Mineral Habits?

What are Crystal Systems and Mineral Habits?

Crystals have habits. In crystallography, mineral habits refer to the way crystals form within a specific mineral. There are six...
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Gemstone Hardness and Wearability

Gemstone Hardness and Wearability

Gemstone hardness measures resistance to scratching. A gem's wearability grade takes hardness into account, but it’s only one of many...
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Australian Opals

Australian Opals

Australian opals account for 95% of the world’s supply. Learn about Australia’s geological history, the start of its opal trade,...
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Opal Wearability and Jewelry Tips

Opal Wearability and Jewelry Tips

Are opals too delicate for jewelry? Learn how to choose the right settings for opal wearability, so you can enjoy...
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Guide to Organizing Your Gemstone Collection

Guide to Organizing Your Gemstone Collection

Learn how to organize your gemstone collection. Choose the storage and display options that are right for you and create...
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Take the Birthstone Quiz

Take the Birthstone Quiz

What do you know about birthstones? Take our short birthstone quiz and learn about the makeup, cutting, and value of...
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How to Start a Gem Collection

How to Start a Gem Collection

Although many gem enthusiasts want to become collectors, they may not know where to begin. Read this article for tips...
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Understanding Gemological Formulas

Understanding Gemological Formulas

Gemological formulas identify the chemical composition of gems and minerals. Learn what the symbols, numbers, and parentheses mean.
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What is Gemstone Luster?

What is Gemstone Luster?

Gemstone luster describes how a gem's surface looks when it reflects light. Learn the common terms gemologists use for this...
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What is a Gem?

What is a Gem?

Even the most general definition of a gem has many exceptions. Learn what qualities have been used to identify gemstones...
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A Guide to Gem Classification

A Guide to Gem Classification

Gemologists use several different gem classification methods. Learn how the most common systems work and what they cover as well...
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What are Allochromatic and Idiochromatic Gems?

What are Allochromatic and Idiochromatic Gems?

Learn the difference between allochromatic and idiochromatic gems and why some gem species can occur in many color varieties and...
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Mechanical Gemstone Cleaning

Mechanical Gemstone Cleaning

Mechanical gemstone cleaning has benefits and risks. Learn all about ultrasonic, steam, and boiling systems and how gems might react...
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What is Gemstone Dispersion?

What is Gemstone Dispersion?

Learn what gemstone dispersion means, what causes it, and how it relates to other optical effects.
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What are Gem Species and Gem Varieties?

What are Gem Species and Gem Varieties?

Gem species are mineral species prized for their durability and beauty. Learn how chemical formulas and crystal structures define species...
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How Do Aquamarines Form?

How Do Aquamarines Form?

The March birthstone, aquamarine is a popular gem. Learn how aquamarines form, what they look like, and how they get...
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Trapiche Gems: An Introduction

Trapiche Gems: An Introduction

Satisfying the human desire for symmetry, trapiche gems have a special allure. Learn what makes these rarities so unique in...
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Understanding Gem Synthetics, Treatments, and Imitations, Part 5: Gemstone Treatments

Understanding Gem Synthetics, Treatments, and Imitations, Part 5: Gemstone Treatments

Identifying gemstone treatments is difficult even for experienced gemologists. Learn about the many different ways gem color and clarity are...
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What is a Crystal?

What is a Crystal?

Learn the scientific definition of crystal used by gemologists and answer some basic questions about what is and is not...
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What is a Gem Reflectometer?

What is a Gem Reflectometer?

What’s the difference between a reflectometer and a refractometer? If you’re interested in studying or buying gems, learn the facts...
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What are Gemstone Absorption Spectra?

What are Gemstone Absorption Spectra?

Learn how gems absorb wavelengths of light and how gemologists use gemstone absorption spectra to identify gems. There’s more to...
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Recommended Gemology Tools and Instruments

Recommended Gemology Tools and Instruments

Gemstone identification requires a good reference library and some basic gemology tools. Before you go shopping, learn more about what...
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Spectroscope Instructions for Novice Gemologists

Spectroscope Instructions for Novice Gemologists

The spectroscope is one of gemology’s principal tools. Our basic spectroscope instructions will teach you how to operate and calibrate...
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How Do Garnets Form?

How Do Garnets Form?

A versatile gem and the famous January birthstone, garnet is a favorite among jewelers and consumers. Learn how garnets form...
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How to Clean Your Gemstone Jewelry

How to Clean Your Gemstone Jewelry

A little gemology goes a long way. Learn how to clean your gemstone jewelry safely and how to deal with...
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How Does Quartz Form?

How Does Quartz Form?

Quartz is one of the most abundant minerals on earth. Learn how quartz forms and how its most popular varieties...
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How Does Topaz Form?

How Does Topaz Form?

Topaz requires specific and unusual conditions to form. Learn how topaz develops and how it gets its colors, from yellow...
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How Do Tourmalines Form?

How Do Tourmalines Form?

Tourmalines are a large mineral group with a variety of chemical compositions. Learn how tourmalines form and why so many...
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How Do Emeralds Form?

How Do Emeralds Form?

How do emeralds form? Learn how the emerald growth process works and why it makes these gems rare, green, and...
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What’s the Difference Between Rubies and Pink Sapphires?

What’s the Difference Between Rubies and Pink Sapphires?

How do gemologists distinguish between rubies and pink sapphires? Learn about the chemistry of corundum and the history of the...
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How Do Rubies and Sapphires Form?

How Do Rubies and Sapphires Form?

The geological conditions in which rubies and sapphires form are rare and extreme. Learn how these popular gems develop and...
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Keshi Pearls and Soufflé Pearls

Keshi Pearls and Soufflé Pearls

Not all pearls are perfectly round and white. Learn about keshi pearls and soufflé pearls, two beautiful byproducts of the...
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Tahitian Pearls: Beautiful Black Pearls

Tahitian Pearls: Beautiful Black Pearls

With dark bodies and colorful sheens, beautiful Tahitian pearls have mesmerized jewelry lovers for decades. Learn more about these and...
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South Sea Pearls: the Complete Guide

South Sea Pearls: the Complete Guide

With thick nacre and large sizes, South Sea pearls really stand out when compared to other pearl types. Learn more...
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Freshwater Cultured Pearls

Freshwater Cultured Pearls

As consumers compare price and quality, freshwater cultured pearls are rapidly becoming more popular than Akoyas. Learn more about these...
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Akoya Pearls: the Complete Guide

Akoya Pearls: the Complete Guide

Since the beginning of the cultured pearl industry, Akoya pearls have ruled the market. Learn more about the quintessential round,...
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How Do Pearls Form?

How Do Pearls Form?

Do pearls form around grains of sand trapped in oysters? Learn the facts about pearl formation and the various mollusks...
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Uncommon Elements Make Uncommon Gemstones

Uncommon Elements Make Uncommon Gemstones

Why are some gems so rare in nature? Learn which elements in the Earth’s crust are the rarest and how...
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Desert Prospecting: Discovering California Turquoise

Desert Prospecting: Discovering California Turquoise

IGS member Richard Edley shares his experiences discovering California turquoise and offers advice on desert prospecting.
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How Do Opals Form?

How Do Opals Form?

Curious about how opals form and show such stunning colors? Learn about the scientific theories behind opal formation and why...
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Gemology Career Options

Gemology Career Options

Thinking of becoming a gemologist? Consider these gemology career options, compare their estimated salaries, and decide which one may be...
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An Introduction to Gemology

An Introduction to Gemology

Learn what gemologists do in our introduction to gemology. Whether your interest is casual or professional, the world of gems...
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What is Gemstone Transparency?

What is Gemstone Transparency?

Gemstone transparency describes how much light passes through a gem and how it scatters. Learn what causes a gem to...
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A Brief History of Diamonds

A Brief History of Diamonds

Learn how diamonds formed geologically and how they became the virtual standard for engagement ring stones in this brief history...
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Opal and Pearl Care Guide

Opal and Pearl Care Guide

Opals and pearls have special setting, cleaning, and storage needs. Our opal and pearl care guide will help you keep...
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What is Gemstone Birefringence?

What is Gemstone Birefringence?

Gemstone birefringence is a measure of a gem's double refraction. Learn how it’s used to identify gems and see the...
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An Introduction to Fancy Gem Cuts

An Introduction to Fancy Gem Cuts

Rounds dominate the gem market, but fancy gem cuts offer many beautiful options. Learn about the most popular fancy shapes,...
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A Guide to Gem Cutting Styles

A Guide to Gem Cutting Styles

Gem cutting styles refer to the shape and arrangement of facets. The three most basic styles are brilliant, step, and...
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Gemstone Facets: Terminology and Functions

Gemstone Facets: Terminology and Functions

Not only do gemstone facets create beautiful patterns on gem surfaces, they also help gems shine. While gem cutters will...
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An Introduction to the Lapidary Arts

An Introduction to the Lapidary Arts

Lapidary is the art of working with gemstones. Learn more about the four basic lapidary arts: tumbling, cabbing, faceting, and...
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Basics of Gemstone Density and Specific Gravity

Basics of Gemstone Density and Specific Gravity

Gemologists sometimes measure gemstone density or specific gravity to help with gem identification. Learn the basics of this property and...
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Precision Faceting a Story Gemstone: Custom Faceting Advice

Precision Faceting a Story Gemstone: Custom Faceting Advice

Your prized gemstones deserve custom faceting. Learn the benefits of working with precision faceters and tips for starting your own...
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Precision Faceting A Story Gemstone: The Faceting Process

Precision Faceting A Story Gemstone: The Faceting Process

The faceting process turns rough stones into finished gems. Learn the steps custom faceters take to create unique gemstones that...
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Precision Faceting A Story Gemstone: Faceting Equipment

Precision Faceting A Story Gemstone: Faceting Equipment

Today's custom gem cutters use faceting equipment for precision work and design inspiration. Take a look at the toolkit of...
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Precision Faceting A Story Gemstone: Gem Design

Precision Faceting A Story Gemstone: Gem Design

In the gem design stage of jewelry making, faceters evaluate a stone's qualities. Learn how to choose a cut for...
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Precision Faceting A Story Gemstone: Choosing Rough

Precision Faceting A Story Gemstone: Choosing Rough

A precision faceter can turn a rough stone into a story gemstone as unique as each client. Choosing the right...
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IGS Certification Exam: Sample Gemology Questions

IGS Certification Exam: Sample Gemology Questions

What does it take to become a professional gemologist? Try these sample gemology questions from the International Gem Society certification...
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Sphalerite Appraisal

Sphalerite Appraisal

Learn what factors most influence a sphalerite appraisal and what kind of jewelry will best showcase this beautiful gemstone.
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Understanding Gem Synthetics, Treatments, And Imitations, Part 2: Crystal Growth

Understanding Gem Synthetics, Treatments, And Imitations, Part 2: Crystal Growth

Learn about the different crystal growth methods used to artificially create gemstones in laboratories.
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Understanding Gem Synthetics, Treatments, And Imitations, Part 3: Synthetic Diamond

Understanding Gem Synthetics, Treatments, And Imitations, Part 3: Synthetic Diamond

Learn about synthetic diamond creation and the challenges buyers face determining whether a diamond is natural or artificial.
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Understanding Gem Synthetics, Treatments, And Imitations, Part 4: Synthetic Gemstone Guide

Understanding Gem Synthetics, Treatments, And Imitations, Part 4: Synthetic Gemstone Guide

Many varieties of gems besides diamond can be created in the laboratory. Our synthetic gemstone guide covers many examples and...
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Build Your Own Gemology Tools

Build Your Own Gemology Tools

Are you a hobbyist or professional gemologist facing high equipment costs? Read our IGS series of articles that can help...
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Understanding Gem Synthetics, Treatments, And Imitations, Part 1: An Introduction

Understanding Gem Synthetics, Treatments, And Imitations, Part 1: An Introduction

Tech advances and market forces make it essential for gem buyers to know the science behind synthetic gemstones and gem...
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